Crystals

18 pages, 402 KiB

Open AccessArticle

A Visual Representation for Accurate Local Basis Set Construction and Optimization: A Case Study of SrTiO₃ with Hybrid DFT Functionals

by Guntars Zvejnieks, Leonid L. Rusevich, Eugene Heifets, Eugene Kotomin and Denis Gryaznov

Crystals 2024, 14(7), 671; https://doi.org/10.3390/cryst14070671 - 22 Jul 2024

Viewed by 651

Abstract

The linear combination of atomic orbitals (LCAO) method is advantageous for calculating important bulk and surface properties of crystals and defects in/on them. Compared to plane wave calculations and contrary to common assumptions, hybrid density functional theory (DFT) functionals are actually less costly [...] Read more.

The linear combination of atomic orbitals (LCAO) method is advantageous for calculating important bulk and surface properties of crystals and defects in/on them. Compared to plane wave calculations and contrary to common assumptions, hybrid density functional theory (DFT) functionals are actually less costly and easier to implement in LCAO codes. However, choosing the proper basis set (BS) for the LCAO calculations representing Guassian-type functions is crucial, as the results depend heavily on its quality. In this study, we introduce a new basis set (BS) visual representation, which helps us (1) analyze the collective behavior of individual atoms’ shell exponents (s, p, and d), (2) better compare different BSs, (3) identify atom-type invariant relationships, and (4) suggest a robust method for building a local all-electron BS (denoted as BS1) from scratch for each atom type. To compare our BS1 with the others existing in the literature, we calculate the basic bulk properties of

{SrTiO}_{3}

(STO) in cubic and tetragonal phases using several hybrid DFT functionals (B3LYP, PBE0, and HSE06). After adjusting the exact Hartree–Fock (HF) exchange of PBEx, HSEx, and the state-of-the-art meta-GGA hybrid

r^{2}

SCANx functionals, we find the

r^{2}

SCAN15 and HSE27 for BS1, with the amount of exact HF exchange of 0.15 and 0.27, respectively, perform equally well for reproducing several most relevant STO properties. The proposed robust BS construction scheme has the advantage that all parameters of the obtained BS can be reoptimized for each new material, thus increasing the quality of DFT calculation predictions. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

► Show Figures

Figure 1

24 pages, 6688 KiB

Open AccessArticle

Synthesis, Characterization, and Analysis of Probenecid and Pyridine Compound Salts

by Menglong Zhang, Xinyu Hou, Fuhai Yu, Liang Zhang, Baohong Hou, Lina Zhou, Chuang Xie, Songgu Wu and Wei Chen

Crystals 2024, 14(7), 670; https://doi.org/10.3390/cryst14070670 - 22 Jul 2024

Viewed by 744

Abstract

This study aimed to address the issue of the low solubility in the model drug probenecid (PRO) and its impact on bioavailability. Two salts of probenecid (PRO), 4-aminopyridine (4AMP), and 4-dimethylaminopyridine (4DAP) were synthesized and characterized by PXRD, DSC, TGA, FTIR, and SEM. [...] Read more.

This study aimed to address the issue of the low solubility in the model drug probenecid (PRO) and its impact on bioavailability. Two salts of probenecid (PRO), 4-aminopyridine (4AMP), and 4-dimethylaminopyridine (4DAP) were synthesized and characterized by PXRD, DSC, TGA, FTIR, and SEM. The crystal structures of the two salts were determined by SCXRD, demonstrating that the two salts exhibited different hydrogen bond networks, stacking modes, and molecular conformations of PRO. The solubility of PRO and its salts in a phosphate-buffered solution (pH = 6.8) at 37 °C was determined, the results showed that the solubility of PRO salts increased to 142.83 and 7.75 times of the raw drug, respectively. Accelerated stability experiments (40 °C, 75% RH) showed that the salts had good phase stability over 8 weeks. Subsequently, Hirshfeld surface (HS), atom in molecules (AIM), and independent gradient model (IGM) were employed for the assessment of intermolecular interactions. The analyses of salt-forming sites and principles were conducted using molecular electrostatic potential surfaces (MEPs) and pK_a rules. The lattice energy (E_L) and hydration-free energy (E_HF) of PRO and its salts were calculated, and the relationships between these parameters and melting points and the solubility changes were analyzed. Full article

(This article belongs to the Section Crystal Engineering)

► Show Figures

Graphical abstract

18 pages, 14498 KiB

Open AccessArticle

Evolution of the Microstructure, Phase Composition and Thermomechanical Properties of the CuZnIn Alloys, Achieved by Thermally Controlled Phase Transitions

by Anna Sypien, Tomasz Czeppe, Anna Wojcik, Grzegorz Garzel, Anna Goral, Marek Kopyto and Zbigniew Swiatek

Crystals 2024, 14(7), 669; https://doi.org/10.3390/cryst14070669 - 22 Jul 2024

Viewed by 710

Abstract

Ternary alloys with CuZnIn compositions based on the binary CuZn diagram and the modeled ternary system solidus projection were investigated. The as-cast alloys, hot-rolled sheets, and samples annealed at low temperature were examined. It was found that the α-CuZn solution phase, with minor [...] Read more.

Ternary alloys with CuZnIn compositions based on the binary CuZn diagram and the modeled ternary system solidus projection were investigated. The as-cast alloys, hot-rolled sheets, and samples annealed at low temperature were examined. It was found that the α-CuZn solution phase, with minor indium additions (1–2% at.), was the primary phase crystallizing during casting and remained stable at low temperatures. The ternary phase with an approximate composition of Cu₈(In,Zn)_4.5 and a structure analogous to the high-temperature γ-Cu₉In₄ phase crystallized from the liquid state and remained stable at low temperatures. This behavior results from the stabilization against peritectoidal decomposition by the Zn atoms when substituting In in the structure. A new phase γ*-Cu₉(In,Zn)₄ with a modified structure was identified, characterized by a reduced unit cell and an altered electronic structure. The hot-rolling process preserves the phase composition and forms a composite-like structure, with the matrix composition of γ* and large ellipsoidal α-CuZn solution particles. On a microscale, the γ* matrix exhibited a specific structure resulting from segregation processes and was composed of micrometer-sized α-CuZn(In) solution particles and nano-sized β-CuZn phase precipitates. Low-temperature annealing intensifies the γ* matrix decomposition through binary phase precipitation. Full article

(This article belongs to the Special Issue Advanced Crystalline Materials, Mechanical Properties and Innovative Production Systems (2nd Edition))

► Show Figures

Figure 1

13 pages, 3717 KiB

Open AccessArticle

Numerical Modeling of Hybrid Solar/Thermal Conversion Efficiency Enhanced by Metamaterial Light Scattering for Ultrathin PbS QDs-STPV Cell

by Oussama Baitiche, Fathi Bendelala, Ali Cheknane, Abdelaziz Rabehi and Elisabetta Comini

Crystals 2024, 14(7), 668; https://doi.org/10.3390/cryst14070668 - 21 Jul 2024

Cited by 5 | Viewed by 1735

Abstract

Ultrathin cells are gaining popularity due to their lower weight, reduced cost, and enhanced flexibility. However, compared to bulk cells, light absorption in ultrathin cells is generally much lower. This study presents a numerical simulation of a metamaterial light management structure made of [...] Read more.

Ultrathin cells are gaining popularity due to their lower weight, reduced cost, and enhanced flexibility. However, compared to bulk cells, light absorption in ultrathin cells is generally much lower. This study presents a numerical simulation of a metamaterial light management structure made of ultrathin lead sulfide colloidal quantum dots (PbS CQDs) sandwiched between a top ITO grating and a tungsten backing to develop an efficient hybrid solar/thermophotovoltaic cell (HSTPVC). The optical properties were computed using both the finite integration technique (FIT) and the finite element method (FEM). The absorptance enhancement was attributed to the excitations of magnetic polaritons (MP), surface plasmon polaritons (SPP), and lossy mode resonance (LMR). The HSTPVC with the metamaterial optical light management structure was assessed for short-circuit current density, open-circuit voltage, and conversion efficiency. The results show a conversion efficiency of 18.02% under AM 1.5 solar illumination and a maximum thermophotovoltaic conversion efficiency of 12.96% at TB = 1600 K. The HSTPVC can operate in a hybrid solar/thermal conversion state when the ITO grating is included by combining the advantages of QDs and metamaterials. This work highlights the potential for developing a new generation of hybrid STPV cells through theoretical modeling and numerical simulations. Full article

(This article belongs to the Section Hybrid and Composite Crystalline Materials)

► Show Figures

Figure 1

14 pages, 2542 KiB

Open AccessArticle

Hydroxyapatite Reinforced Magnesium Alloy Composites Using the Ultrasonic-Assisted Rheo-Squeeze Casting Technique: Microstructural and Mechanical Performance Evaluation for Bone Fixture Applications

by Arunkumar Thirugnanasambandam, Ashokkumar Mohankumar, Rajendra Prasad Reddy Botta, William Woei Fong Chong, Geethapriyan Thangamani and Manoj Gupta

Crystals 2024, 14(7), 667; https://doi.org/10.3390/cryst14070667 - 21 Jul 2024

Viewed by 818

Abstract

Magnesium-based biomaterials have recently been in the research spotlight in the field of biomedical engineering owing to their properties, such as density and biocompatibility that closely align with those of human bone. However, poor strength and rapid degradation impede their application as bone [...] Read more.

Magnesium-based biomaterials have recently been in the research spotlight in the field of biomedical engineering owing to their properties, such as density and biocompatibility that closely align with those of human bone. However, poor strength and rapid degradation impede their application as bone support fixtures. The present research aims to tailor the properties of Mg by using a novel ultrasonic-assisted rheo-squeeze casting approach. To satisfy the demand, pure Mg (Mg), MHA (Mg/5%HA), MZHA (Mg-1%Zn/5%HA/), and MSHA (Mg-1%Sn/5%HA) were fabricated, and various mechanical tests were conducted to assess the composite’s mechanical properties, including its microhardness, tensile strength, compressive strength, flexural strength, and impact strength. The microstructural and fractured morphology of the composites was examined by scanning electron microscopy (SEM), whereas their elemental composition was analyzed by field emission scanning electron microscopy (FESEM) equipped with elemental mapping. Comparing the MZHA, MHA, and pure Mg samples, the mechanical behavior of MSHA is significantly superior. This is due to composites containing Sn that possess finer-grained materials, which act as barriers to dislocation motion while increasing the strength of the materials. From the observed results, there is a significant improvement in the microhardness of MSHA of 64.5% when compared to that of pure Mg, and 42.7% compared to MHA. Furthermore, MSHA composites possess noticeable enhancements in tensile and compression performance of 80.8% and 58.3%, respectively, and 19% and 22.4% compared to MHA. Additionally, the impact and flexural performance of MSHA composites exhibit higher performance (41% and 42%) than pure Mg and 8% and 7% against the MHA composite. Full article

(This article belongs to the Special Issue Corrosion and Mechanical Performance of Magnesium Alloys)

► Show Figures

Figure 1

4 pages, 169 KiB

Open AccessEditorial

Understanding Processing–Microstructure–Property Relationships of Structural Alloys

by Qing-Qiang Ren

Crystals 2024, 14(7), 666; https://doi.org/10.3390/cryst14070666 - 20 Jul 2024

Viewed by 622

Abstract

Although intensively investigated for centuries, structural alloys, especially steels, continue to attract a great deal of research interest [...] Full article

(This article belongs to the Special Issue Microstructure and Properties of Steels and Other Structural Alloys)

44 pages, 14022 KiB

Open AccessReview

Advancements and Perspectives in Additive Manufacturing of Tungsten Alloys and Composites: Challenges and Solutions

by Mehrdad Zarinejad, Yunxiang Tong, Mojtaba Salehi, Chengfa Mu, Nian Wang, Yonglong Xu, Sajjad Rimaz, Lintao Tian, Kai Xiang Kuah and Xiaotong Chen

Crystals 2024, 14(7), 665; https://doi.org/10.3390/cryst14070665 - 20 Jul 2024

Viewed by 1329

Abstract

This review explores additive manufacturing (AM) for refractory tungsten (W) and its alloys, highlighting the primary challenges and determining factors in the AM of pure W, W alloys and composites. The challenges mainly arise from W’s high melting point, low laser absorptivity, high [...] Read more.

This review explores additive manufacturing (AM) for refractory tungsten (W) and its alloys, highlighting the primary challenges and determining factors in the AM of pure W, W alloys and composites. The challenges mainly arise from W’s high melting point, low laser absorptivity, high thermal conductivity, high melt viscosity, high oxygen affinity, high ductile-to-brittle transition temperature, and inherent embrittlement, which lead to defects and anomalies in AM-produced parts. This review focuses on both processes and alloying strategies to address the issues related to densification, micro-cracking, and the resultant properties in W-based components. Cracking in additively manufactured W remains a persistent issue due to thermal stress, embrittlement, and oxide formation. Powder characteristics, process parameters, and thermal management strategies are crucial for W densification. Throughout the review, existing knowledge and insights are organized into comprehensive tables, serving as valuable resources for researchers delving deeper into this topic. Future research in W-AM should focus on understanding the interaction between AM process parameters and microstructural and material design. Advances in atomic-level understanding, thermodynamic modeling, and data analytics have the potential to significantly enhance the precision, sustainability, and applicability of W-AM. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Structural Materials)

► Show Figures

Figure 1

11 pages, 12136 KiB

Open AccessArticle

Solvent-Dependent Triboelectric Output Performance of Poly(vinylidene fluoride–trifluoroethylene–chlorofluoroethylene) Terpolymer

by Ying Chieh Hu, Hyun Soo Ahn, Joo Hyeong Lee, Kyung Hoon Kim, Jong Hun Kim and Jong Hoon Jung

Crystals 2024, 14(7), 664; https://doi.org/10.3390/cryst14070664 - 19 Jul 2024

Viewed by 711

Abstract

The poly (vinylidene fluoride–trifluoroethylene–chlorofluoroethylene) P(VDF-TrFE-CFE) terpolymer has been identified as a promising candidate for the effective conversion of low-frequency mechanical vibrations into electricity. In this study, we provide a comprehensive and systematic investigation of the solvent-dependent mechanical, microstructural, electrical, frictional properties and triboelectric [...] Read more.

The poly (vinylidene fluoride–trifluoroethylene–chlorofluoroethylene) P(VDF-TrFE-CFE) terpolymer has been identified as a promising candidate for the effective conversion of low-frequency mechanical vibrations into electricity. In this study, we provide a comprehensive and systematic investigation of the solvent-dependent mechanical, microstructural, electrical, frictional properties and triboelectric output performance of a relaxor ferroelectric P(VDF-TrFE-CFE) terpolymer. The P(VDF-TrFE-CFE) terpolymer films obtained from high dipole moment solvents have a longer rod-shaped grain than those from low dipole moment solvents. The crystallinity, Young’s modulus and dielectric constant of P(VDF-TrFE-CFE) terpolymer become larger as the dipole moment of solvents increases, while the remnant polarization remains almost the same. The P(VDF-TrFE-CFE) terpolymer film obtained from the highest dipole moment solvent generates almost 1.55 times larger triboelectric charge than that obtained from the lowest moment. We attributed this large difference to the greatly enhanced lateral friction of terpolymer film obtained from high dipole moment solvents. Full article

(This article belongs to the Special Issue Emerging Applications of Ferroelectrics in Nanoelectronics and Renewable Energy)

► Show Figures

Graphical abstract

11 pages, 3229 KiB

Open AccessArticle

Understanding Avobenzone Crystallization in Sunscreen Formulations: Role of Metal Oxide-Driven Nucleation and Stabilization Strategies

by Olga Goral, Grazyna Zofia Zukowska, Elzbieta Zero, Maciej Siekierski and Anna Krzton-Maziopa

Crystals 2024, 14(7), 663; https://doi.org/10.3390/cryst14070663 - 19 Jul 2024

Viewed by 1073

Abstract

The crystallization behavior of avobenzone in cosmetic formulations has been investigated with a focus on its interaction with titanium dioxide and zinc oxide particles. Characterization studies using SEM, powder X-ray diffraction (PXRD), Raman spectroscopy, and energy-dispersive X-ray spectroscopy (EDS) reveal that avobenzone undergoes [...] Read more.

The crystallization behavior of avobenzone in cosmetic formulations has been investigated with a focus on its interaction with titanium dioxide and zinc oxide particles. Characterization studies using SEM, powder X-ray diffraction (PXRD), Raman spectroscopy, and energy-dispersive X-ray spectroscopy (EDS) reveal that avobenzone undergoes crystallization facilitated by nucleation on the surfaces of these metal oxide grains. The presence of wax and titanium oxide within the crystalline structures further suggests a complex formation, potentially involving catalytic effects on avobenzone nucleation and isomerization. Notably, the addition of ascorbyl palmitate inhibits unwanted crystallization, possibly through competitive complexation with exposed metal ions. These findings underscore the significance of formulation modifications in stabilizing avobenzone against crystallization, ensuring enhanced product stability in cosmetic applications. Future structural studies are anticipated to elucidate the precise nature of these co-crystalline phases, offering insights into optimizing sunscreen formulations for improved performance and longevity. Full article

(This article belongs to the Topic Modern Material Technologies Intended for Industrial Applications)

► Show Figures

Figure 1

18 pages, 4150 KiB

Open AccessArticle

Two Modifications of Nitrilotris(methylenephenylphosphinic) Acid: A Polymeric Network with Intermolecular (O=P–O–H)₃ vs. Monomeric Molecules with Intramolecular (O=P–O–H)₃ Hydrogen Bond Cyclotrimers

by Steven Knerr, Erica Brendler, Robert Gericke, Edwin Kroke and Jörg Wagler

Crystals 2024, 14(7), 662; https://doi.org/10.3390/cryst14070662 - 19 Jul 2024

Cited by 1 | Viewed by 813

Abstract

Nitrilotris(methylenephenylphosphinic) acid (NTPAH₃) was silylated using hexamethyldisilazane to produce the tris(trimethylsilyl) derivative NTPA(SiMe₃)₃. From the latter, upon alcoholysis in chloroform, NTPAH₃ could be recovered. Thus, a new modification of that phosphinic acid formed. Meanwhile, NTPAH [...] Read more.

Nitrilotris(methylenephenylphosphinic) acid (NTPAH₃) was silylated using hexamethyldisilazane to produce the tris(trimethylsilyl) derivative NTPA(SiMe₃)₃. From the latter, upon alcoholysis in chloroform, NTPAH₃ could be recovered. Thus, a new modification of that phosphinic acid formed. Meanwhile, NTPAH₃ synthesized in aqueous hydrochloric acid crystallized in the space group P3c1 with the formation of O-H⋅⋅⋅O H-bonded networks (NTPAH₃^P), in chloroform crystals in the space group R3c formed (NTPAH₃^M), the constituents of which are individual molecules with exclusively intramolecular O-H⋅⋅⋅O hydrogen bonds. Both solids, NTPAH₃^P and NTPAH₃^M, were characterized by single-crystal X-ray diffraction, multi-nuclear (¹H, ¹³C, ³¹P) solid-state NMR spectroscopy, and IR spectroscopy as well as quantum chemical calculations (both of their individual constituents as isolated molecules as well as in the periodic crystal environment). In spite of the different stabilities of their constituting molecular conformers, the different crystal packing interactions rendered the modifications of NTPAH₃^P and NTPAH₃^M similarly stable. In both solids, the protons of the acid are engaged in cyclic (O=P–O–H)₃ H-bond trimers. Thus, the trialkylamine N atom of this compound is not protonated. IR and ¹H NMR spectroscopy of these solids indicated stronger H-bonds in the (O=P–O–H)₃ H-bond trimers of NTPAH₃^M over those in NTPAH₃^P. Full article

(This article belongs to the Special Issue Different Kinds of Hydrogen Bonds in Crystal Structures)

► Show Figures

Graphical abstract

11 pages, 3178 KiB

Open AccessReview

Photo-Induced Degradation of Priority Air Pollutants on TiO₂-Based Coatings in Indoor and Outdoor Environments—A Mechanistic View of the Processes at the Air/Catalyst Interface

by Dimitrios Kotzias

Crystals 2024, 14(7), 661; https://doi.org/10.3390/cryst14070661 - 19 Jul 2024

Viewed by 862

Abstract

In recent decades, numerous studies have indicated the substantial role semiconductors could play in photocatalytic processes for environmental applications. Materials that contain a semiconductor as a photocatalyst have a semi-permanent capacity for removing harmful gases from the ambient air. In this paper, the [...] Read more.

In recent decades, numerous studies have indicated the substantial role semiconductors could play in photocatalytic processes for environmental applications. Materials that contain a semiconductor as a photocatalyst have a semi-permanent capacity for removing harmful gases from the ambient air. In this paper, the focus is on TiO₂. Heterogeneous photocatalysis using TiO₂ leads to the degradation of NO/NO₂, benzene, toluene, and other priority air pollutants once in contact with the semiconductor surface. Preliminary evidence indicates that TiO₂-containing construction materials and paints efficiently destroy the ozone precursors NO and NO₂ by up to 80% and 30%, respectively. Therefore, the development of innovative coatings containing TiO₂ as a photocatalyst was in the foreground of research activities. The aim of this was for coatings to be used as building and construction materials, mainly outdoors, e.g., on building façades on high-traffic roads for the degradation of priority air pollutants (NOx and volatile organic compounds) in the polluted urban atmosphere. Though there are advantages connected with the application of TiO_2, due to its band gap of 3.2 eV, these are limited. TiO₂ is effective only in the UV region (ca. 5%) of the solar spectrum with wavelengths λ < 380 nm. Hence, efforts are made here, as in many research studies, to dope TiO₂ with transition metals to increase its activity using visible light, which will extend its application to indoor environments. In our studies, experiments were conducted with 0.1% (w/w) and 1% (w/w) Mn-TiO₂ admixtures, and the ability of the modified photocatalysts to degrade NO by both solar and indoor illumination was evaluated. The surface chemistry at the air/catalyst interface, governed by the photoelectric characteristics of TiO₂ and the formation of reactive oxygen species with co-occurring redox reactions, is reviewed in this paper. The factors affecting the application of TiO₂ for the degradation of priority air pollutants as single compounds or mixtures are discussed. We investigated, particularly, the degradation of mixtures of priority compounds at typical concentrations in ambient air and confined spaces. This is a realistic approach, because pollutants are present as mixtures, rather than as individual compounds in ambient and indoor air. Moreover, organic polymers as paint constituents were found to be the primary source for carbonyl formation, e.g., formaldehyde, acetaldehyde, etc., during the heterogeneous photocatalytic processes conducted on TiO₂-enriched coatings. Full article

(This article belongs to the Special Issue Nanomaterials for Environmental and Solar Energy Applications)

► Show Figures

Figure 1

16 pages, 5676 KiB

Open AccessArticle

Chitosan–Alginate Nanocontainers with Caffeine as Green Corrosion Inhibitors for Protection of Galvanized Steel

by Kamelia Kamburova, Nelly Boshkova, Tsetska Radeva, Maria Shipochka and Nikolai Boshkov

Crystals 2024, 14(7), 660; https://doi.org/10.3390/cryst14070660 - 19 Jul 2024

Cited by 3 | Viewed by 1030

Abstract

The introduction of new regulations needs to develop eco-friendly systems to prevent corrosion. In this work, a natural corrosion inhibitor caffeine (CAF) was encapsulated in polysaccharide-based nanoparticles, capable of the responsive release of CAF during corrosion. The nanoparticles were prepared using electrostatic complexation [...] Read more.

The introduction of new regulations needs to develop eco-friendly systems to prevent corrosion. In this work, a natural corrosion inhibitor caffeine (CAF) was encapsulated in polysaccharide-based nanoparticles, capable of the responsive release of CAF during corrosion. The nanoparticles were prepared using electrostatic complexation between two natural polysaccharides which are oppositely charged—chitosan (CHI) and sodium alginate (ALG), crosslinked by tripolyphosphate (TPP). The particle size distribution and zeta potential were evaluated using dynamic light scattering and laser Doppler velocimetry. The encapsulation efficiency and release of CAF from nanocontainers was evaluated with UV-spectroscopy. The nanoparticles were incorporated via electrodeposition into the zinc coating on low-carbon steel to ensure self-healing. Cyclic voltammetry demonstrated the cathodic and anodic processes in the starting electrolytes. Surface hydrophobicity was investigated by water contact angle (WCA). The corrosion resistance of the coatings was estimated with polarization resistance (Rp) measurements and potentiodynamic polarization (PDP) curves. The study of the chemical composition of the coatings was carried out with X-ray photoelectron spectroscopy. The data obtained confirm the indisputable influence of the nanoparticles/nanocontainers on the protective feature of the hybrids—the latter have about twice-higher Rp values compared to the ordinary zinc. Full article

(This article belongs to the Special Issue Corrosion Phenomena in Metals)

► Show Figures

Figure 1

16 pages, 7844 KiB

Open AccessArticle

Functionalized Palygorskite as a Delivery Platforms for Bioactive Asymmetric Beta-Diketone Dyes

by Florentina Monica Raduly, Valentin Raditoiu, Alina Raditoiu, Maria Grapin, Radu Claudiu Fierascu, Iuliana Raut and Mariana Constantin

Crystals 2024, 14(7), 659; https://doi.org/10.3390/cryst14070659 - 18 Jul 2024

Cited by 1 | Viewed by 698

Abstract

Natural clay minerals are among the most versatile materials used in the biomedical field. Palygorskite has found various applications in this field, from the treatment of diarrheal diseases in the past to materials with antibacterial properties and platforms carrying bioactive compounds used in [...] Read more.

Natural clay minerals are among the most versatile materials used in the biomedical field. Palygorskite has found various applications in this field, from the treatment of diarrheal diseases in the past to materials with antibacterial properties and platforms carrying bioactive compounds used in the treatment of diseases, cosmetic and healthcare products in the present. In this study, a possible delivery method of some bioactive asymmetric β-diketonic compounds is presented. Palygorskite modified with amphionic groups (P) and copper ions (PCu) was used as a platform to load bioactive curcumin derivatives (1 and 2). By varying the copper ions, the amounts of charged active compounds were monitored. Studies have shown that the hybrid materials resulting from the loading of 1 and 2 compounds on palygorskite with 30% copper ions (PCu₃₀) can be used as delivery methods for these asymmetric curcumin derivatives, while palygorskite with 50% copper ions(PCu₅₀) loaded with the same type of bioactive compounds has antibacterial properties. Full article

(This article belongs to the Special Issue Hybrid Organic–Inorganic Materials Used to Improve the Environment and Human Health (2nd Edition))

► Show Figures

Figure 1

11 pages, 2653 KiB

Open AccessArticle

An Electrochemical-Cycling-Induced Capacitive Component on the Surface of an Electrophoretic-Deposited Lithium Iron Phosphate Cathode

by Byoung-Nam Park

Crystals 2024, 14(7), 658; https://doi.org/10.3390/cryst14070658 - 18 Jul 2024

Viewed by 814

Abstract

In our research, we apply electrophoretic deposition (EPD) using AC voltage to investigate how high-C-rate electrochemical reactions affect pseudocapacitive charge storage in lithium iron phosphate (LFP) Li-ion batteries. This method significantly raises the battery’s specific capacity, achieving ~90 mAh/g at a 1 C-rate, [...] Read more.

In our research, we apply electrophoretic deposition (EPD) using AC voltage to investigate how high-C-rate electrochemical reactions affect pseudocapacitive charge storage in lithium iron phosphate (LFP) Li-ion batteries. This method significantly raises the battery’s specific capacity, achieving ~90 mAh/g at a 1 C-rate, along with outstanding cycle stability. Although we observe some capacity reduction over numerous cycles, there is a notable increase in the pseudocapacitive contribution to the battery’s charge storage. This is demonstrated by the consistent peak positions and currents during CV and a stable diffusion constant maintained at 9.6 × 10⁻⁹ cm²∙s⁻¹. These findings highlight the battery’s durability, especially in high-demand scenarios. After an extended cycling period of ~500 cycles, the redox peaks related to the Fe²⁺/Fe³⁺ redox processes remain unchanged in terms of magnitude and position, indicating the battery’s excellent reversibility. Full article

(This article belongs to the Special Issue Recent Advances in Electrode Interface Microstructure of Battery)

► Show Figures

Figure 1

16 pages, 8372 KiB

Open AccessArticle

Design and Analysis of K-Band Single-Pole Double-Throw Switches Based on GaAs Technology

by Sida Tang, Xiaoqing Liu, Mengye Cai, Jiahui Guan, Kaili Wang, Peng Li and Jitai Han

Crystals 2024, 14(7), 657; https://doi.org/10.3390/cryst14070657 - 17 Jul 2024

Viewed by 642

Abstract

Two K-band switch circuits, each consisting of a single-pole double-throw (SPDT) switch, have been built using a 0.15 μm GaAs process. One circuit utilizes diode techniques while the other utilizes field effect transistor (FET) techniques. The diode single-pole double-throw switches that have been [...] Read more.

Two K-band switch circuits, each consisting of a single-pole double-throw (SPDT) switch, have been built using a 0.15 μm GaAs process. One circuit utilizes diode techniques while the other utilizes field effect transistor (FET) techniques. The diode single-pole double-throw switches that have been devised exhibit exceptional linearity and are capable of withstanding high power levels. The switches exhibit a return loss of 10 dB or higher, an insertion loss of 3 dB or lower, and operate within a frequency range of 19 GHz to 25 GHz. They have a compact design with a core size of only 1.05 mm² and consume a total power of 136.8 mW. The FET SPDT switch circuits are created utilizing a parallel–parallel quarter-wavelength transmission line architecture. This design allows for a higher power output compared to using a diode. The transistorized single-pole double-throw switch circuit is designed using a parallel–parallel quarter-wavelength transmission line architecture. This design ensures a low insertion loss. By adjusting the length of the transmission line, the circuit can operate in both frequency bands; the K-band and Ka-band. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

► Show Figures

Figure 1

15 pages, 4283 KiB

Open AccessArticle

Ternary Copper(II) Coordination Compounds with Nonpolar Amino Acids and 2,2′-Bipyridine: Monomers vs. Polymers

by Darko Vušak, Katarina Ležaić, Nenad Judaš and Biserka Prugovečki

Crystals 2024, 14(7), 656; https://doi.org/10.3390/cryst14070656 - 17 Jul 2024

Viewed by 762

Abstract

Reactions of copper(II) sulfate with 2,2′-bipyridine (bipy) and amino acids with nonpolar side chains (l-alanine (HAla), l-valine (HVal), or l-phenylalanine (HPhe)) were investigated under different solution-based and mechanochemical methods. Five new ternary coordination compounds were obtained by a solution-based [...] Read more.

Reactions of copper(II) sulfate with 2,2′-bipyridine (bipy) and amino acids with nonpolar side chains (l-alanine (HAla), l-valine (HVal), or l-phenylalanine (HPhe)) were investigated under different solution-based and mechanochemical methods. Five new ternary coordination compounds were obtained by a solution-based synthesis and three of them additionally by the liquid-assisted mechanochemical method: {[Cu(μ-l-Ala)(H₂O)(bipy)]₂SO₄·2H₂O}_n (1a·2H₂O), {[Cu(μ-l-Ala)(H₂O)(bipy)][Cu(l-Ala)(H₂O)(bipy)]SO₄·2.5H₂O}_n (1b·2.5H₂O), {[Cu(μ-l-Val)(H₂O)(bipy)][Cu(l-Val)(H₂O)(bipy)]₃(SO₄)₂·4H₂O}_n (2·4H₂O), [Cu(l-Phe)(H₂O)(bipy)][Cu(l-Phe)(SO₄)(bipy)]∙8H₂O (3·8H₂O), and [Cu(l-Phe)(H₂O)(bipy)][Cu(l-Phe)(SO₄)(bipy)]∙9H₂O (3·9H₂O). The compounds were characterized by single-crystal and powder X-ray diffraction, infrared spectroscopy, and a thermal analysis. Structural studies revealed two structural types, monomeric in 3·8H₂O and 3·9H₂O, polymeric architectures in 1a·2H₂O, and mixed structures (monomeric and polymeric) in 1b·2.5H₂O and 2·4H₂O. The copper(II) ion is either pentacoordinated or hexacoordinated, with an observed Jahn–Teller effect. The crystal structures are based on an intensive network of hydrogen bonds and π interactions. 1a·2H₂O and 2·4H₂O showed substantial in vitro antiproliferative activity toward human hepatocellular carcinoma (HepG2) and moderate activity toward human acute monocytic leukemia cell lines (THP-1). Full article

(This article belongs to the Section Inorganic Crystalline Materials)

► Show Figures

Graphical abstract

24 pages, 9960 KiB

Open AccessReview

Critical Review on Advanced Cooling Strategies in Friction Stir Processing for Microstructural Control

by Md Saad Patel, R. Jose Immanuel, Ariful Rahaman, Mohammad Faseeulla Khan and Mustapha Jouiad

Crystals 2024, 14(7), 655; https://doi.org/10.3390/cryst14070655 - 17 Jul 2024

Viewed by 970

Abstract

Friction stir processing (FSP) stands as an effective approach designed for grain refinement and site-specific microstructural modification. The evolving microstructure during FSP is determined by various variables out of which rate of sample cooling is the key parameter. More often, FSP is conducted [...] Read more.

Friction stir processing (FSP) stands as an effective approach designed for grain refinement and site-specific microstructural modification. The evolving microstructure during FSP is determined by various variables out of which rate of sample cooling is the key parameter. More often, FSP is conducted in naturally flowing air; however, a large number of studies are conducted by researchers across the world; stressing the importance of additional sample cooling strategy for tailoring the material microstructure. Such strategies vary not only in terms of the cooling medium used but also with regard to various other compliant conditions that must be fulfilled for the cooling process to make them successful and economically viable. This work critically reviews the most prevalent methods practiced by various researchers and industries for controlled sample cooling during and after FSP. The underlying mechanisms; advantages; disadvantages; and limitations of each procedure along with the resulting microstructure and material performances are discussed and recommendations are provided Full article

(This article belongs to the Special Issue Additive Manufacturing: Experiments, Simulations and Data-Driven Modelling)

► Show Figures

Figure 1

16 pages, 3131 KiB

Open AccessArticle

Exploring Reduced Graphene Oxide Sheets Stabilized by Cu(II) and Cu(I) Cations in Ethanol

by Aya Jezzini, Anne Davidson, Tayssir Hamieh and Joumana Toufaily

Crystals 2024, 14(7), 654; https://doi.org/10.3390/cryst14070654 - 16 Jul 2024

Cited by 1 | Viewed by 2153

Abstract

In this study, ultrasound treatment was used to exfoliate commercially available graphite flakes into reduced graphene oxide (rGO) dispersed in ethanol. After centrifugation, solid copper chloride trihydrate was added, resulting in a green liquor containing Cu(II), Cu(I), and rGO. These liquors exhibited good [...] Read more.

In this study, ultrasound treatment was used to exfoliate commercially available graphite flakes into reduced graphene oxide (rGO) dispersed in ethanol. After centrifugation, solid copper chloride trihydrate was added, resulting in a green liquor containing Cu(II), Cu(I), and rGO. These liquors exhibited good and rapid photocatalytic activity in the degradation of eosin and bromophenol blue dyes (elimination in a few seconds) under visible-light irradiation. UV–visible spectroscopy confirmed the presence of rGO and Cu species. The size and morphology of the rGO sheets were investigated by several methods (SAXS, wide-angle XRD, SEM, and TEM). Negative UV peaks indicated light emission, which was independently verified by fluorescence. Intense plasmon peaks, with absorbances greater than 10, were observed after adding copper chloride salt. These plasmons were eliminated by a high dilution before the described catalytic tests were performed. Full article

(This article belongs to the Special Issue Advanced Technologies in Graphene-Based Materials)

► Show Figures

Figure 1

15 pages, 9769 KiB

Open AccessArticle

Ag-Coated Super Duplex Stainless Steel AISI2507 with or without Crystallization of Secondary Phase as Advanced Li-Ion Battery Case Material

by Hyeongho Jo, Jung-Woo Ok, Yoon-Seok Lee, Yonghun Je, Shinho Kim, Seongjun Kim, Jinyong Park, Jaeyeong Lee, Byung-Hyun Shin, Jang-Hee Yoon and Yangdo Kim

Crystals 2024, 14(7), 653; https://doi.org/10.3390/cryst14070653 - 16 Jul 2024

Viewed by 991

Abstract

Li-ion batteries used in portable electronic devices and electric vehicles require high safety standards, necessitating the use of high-performance structural materials for battery casings. Super duplex stainless steel (SDSS) is a structural material suitable for portable electronic products owing to its excellent strength [...] Read more.

Li-ion batteries used in portable electronic devices and electric vehicles require high safety standards, necessitating the use of high-performance structural materials for battery casings. Super duplex stainless steel (SDSS) is a structural material suitable for portable electronic products owing to its excellent strength and corrosion resistance. SDSS AISI2507 was used to construct a Li-ion battery casing, a Ag coating was applied via physical vapor deposition (PVD) after the heat treatment of AISI2507 with or without a secondary phase, and the coating thickness was controlled by varying the PVD time. The thickness of the Ag coating layer increased proportionally with time, thereby enhancing the electrical conductivity. The structure and coating behavior were confirmed using FE-SEM, XRD, and GDS. The secondary phase was crystallized by the segregation of the alloy and formed a BCC structure. The FCC lattice structure exhibited excellent coating behavior on the austenite (FCC structure) of AISI2507. Conversely, the secondary phase exhibited low adhesion owing to differences in composition and crystal structure. However, the Ag coating layer on AISI2507 exhibited excellent electrical conductivity, outperforming conventional Ni-plated Li-ion battery casings comprising AISI304. However, the precipitation of the secondary phase must be controlled, as the formation of the secondary phase acts as a factor that decreases electrical conductivity from 58.8 to 53.6 (ICAS) %. The excellent performance of Ag-coated AISI2507 makes it suitable for the fabrication of enhanced Li-ion battery casings. Full article

(This article belongs to the Special Issue Advanced Crystalline Materials, Mechanical Properties and Innovative Production Systems (2nd Edition))

► Show Figures

Figure 1

12 pages, 3853 KiB

Open AccessArticle

An Analysis of Protein Crystals Grown under Microgravity Conditions

by Keegan Jackson, Rebecca Hoff, Hannah Wright, Ashley Wilkinson, Frances Brewer, Amari Williams, Ben Whiteside, Mark R. Macbeth and Anne M. Wilson

Crystals 2024, 14(7), 652; https://doi.org/10.3390/cryst14070652 - 16 Jul 2024

Viewed by 1252

Abstract

Microgravity has been shown to be an excellent tool for protein crystal formation. A retrospective analysis of all publicly available crystallization data, including many that have not yet been published, clearly demonstrates the value of the microgravity environment for producing superior protein crystals. [...] Read more.

Microgravity has been shown to be an excellent tool for protein crystal formation. A retrospective analysis of all publicly available crystallization data, including many that have not yet been published, clearly demonstrates the value of the microgravity environment for producing superior protein crystals. The parameters in the database (the Butler Microgravity Protein Crystal Database, BμCDB) that were evaluated pertain to both crystal morphology and diffraction quality. Success metrics were determined as improvements in size, definition, uniformity, mosaicity, diffraction quality, resolution limits, and B factor. The proteins in the databases were evaluated by molecular weight, protein type, the number of subunits, space group, and Mattew’s Coefficient. Compared to ground experiments, crystals grown in a microgravity environment continue to show improvement across all metrics evaluated. General trends as well as numerical differences are included in the assessment of the BμCDB. The microgravity environment improves crystal formation across a spectrum of metrics and the datasets utilized for this investigation are excellent tools for this evaluation. Full article

(This article belongs to the Section Biomolecular Crystals)

► Show Figures

Graphical abstract

12 pages, 3560 KiB

Open AccessArticle

Environmentally Assisted Cracking of Duplex and Lean Duplex Stainless Steel Reinforcements in Alkaline Medium Contaminated with Chlorides

by Ulises Martin and David M. Bastidas

Crystals 2024, 14(7), 651; https://doi.org/10.3390/cryst14070651 - 16 Jul 2024

Viewed by 797

Abstract

Herein, the corrosion performance of different stainless steel (SS) reinforcing bar grades in alkaline solution is presented, including UNS S32205 duplex stainless steel (DSS), UNS S32304 and UNS S32001 lean DDS (LDSS). The electrochemical dissolution kinetics were studied by potentiodynamic polarization and the [...] Read more.

Herein, the corrosion performance of different stainless steel (SS) reinforcing bar grades in alkaline solution is presented, including UNS S32205 duplex stainless steel (DSS), UNS S32304 and UNS S32001 lean DDS (LDSS). The electrochemical dissolution kinetics were studied by potentiodynamic polarization and the Tafel slope method. The environmentally assisted cracking (EAC) mechanisms of the different SS grades in the presence of Cl⁻ were revealed with the slow strain rate test (SSRT). The higher activation of the anodic branch and the loss of toughness were related to the austenite-to-ferrite phase ratio. UNS S32205 DSS presented the slowest anodic dissolution kinetics, mainly due to the higher austenite content compared to the other LDSS; however, it suffered a more severe EAC than the UNS S32304 LDSS. In the case of UNS S32001 LDSS, even while having the lowest Ni content (i.e., large ferrite α-phase ratio), it experienced the least decrease in elongation as well as low anodic dissolution kinetics for Cl⁻ contents up to 8 wt.%, where the Cl⁻ threshold was reached. Full article

(This article belongs to the Special Issue Corrosion Phenomena in Metals)

► Show Figures

Figure 1

15 pages, 3391 KiB

Open AccessArticle

Potential Nano/Microcenters of Crystal Nucleation in Reagent-Grade Purity Solvents and Their Differentiation by Fluorescent-Tagged Antiscalant

by Konstantin Popov, Yuri Vainer, Gleb Silaev, Vladimir Kuryakov, Maria Trukhina, Elena Koltinova, Vasilii Trokhin, Maxim Oshchepkov, Maria Butakova and Alexander Oshchepkov

Crystals 2024, 14(7), 650; https://doi.org/10.3390/cryst14070650 - 15 Jul 2024

Cited by 1 | Viewed by 811

Abstract

A common issue in studies on liquid-phase chemical processes is that the natural solid nanoimpurities present in reagent-grade chemicals are ignored. Little is known about these impurities’ nature, sizes, concentrations, and behavior, yet they significantly affect the efficiency of antiscalants in municipal and [...] Read more.

A common issue in studies on liquid-phase chemical processes is that the natural solid nanoimpurities present in reagent-grade chemicals are ignored. Little is known about these impurities’ nature, sizes, concentrations, and behavior, yet they significantly affect the efficiency of antiscalants in municipal and laboratory solutions. Recent research has focused on: (i) estimating nanoimpurity concentrations in in-house deionized water and semiconductor-grade isopropanol using “light sheet” optical ultramicroscopy, and (ii) visualizing antiscalant sorption on these impurities. Using a fluorescent-tagged antiscalant aminobis(methylenephosphonic acid) (ADMP-F), we tracked its affinity to particulate matter in deionized water and reagent-grade KCl solutions. Our study showed that the total concentration of nanoparticles with a size larger than 20 nm is about 10⁶ units/mL in deionized water and 10⁵ units/mL in isopropanol. Extrapolation of these values to a size ≥1 nm resulted in concentrations of 10¹¹ and 10⁸ units/mL. The addition of KCl or ADMP-F significantly increased foreign nanoparticle populations. ADMP-F is selectively adsorbed by only some impurities, while most antiscalant molecules remain as true solution. To our knowledge, this is the first instance of fluorescently labeled aminoalkylphosphonates being able to differentiate particulate matter traces in reagent-grade purity solutions. Therefore, the role of nanoparticles as crystallization centers should be seriously reconsidered, especially in their important application in scale inhibition. Full article

(This article belongs to the Section Industrial Crystallization)

► Show Figures

Graphical abstract

31 pages, 8590 KiB

Open AccessArticle

The Biological Crystals in Chamid Bivalve Shells: Diversity in Morphology and Crystal Arrangement Pattern

by Sebastian Hoerl, Erika Griesshaber, Antonio G. Checa and Wolfgang W. Schmahl

Crystals 2024, 14(7), 649; https://doi.org/10.3390/cryst14070649 - 15 Jul 2024

Viewed by 765

Abstract

Chamid bivalves are marine organisms that live in high-energy environments and are cemented to hard substrates. To avoid shell damage, the organisms form thick, densely ornamented shells. Shell material consists of aragonite, and the ornamentation may be either aragonitic or calcitic. The latter [...] Read more.

Chamid bivalves are marine organisms that live in high-energy environments and are cemented to hard substrates. To avoid shell damage, the organisms form thick, densely ornamented shells. Shell material consists of aragonite, and the ornamentation may be either aragonitic or calcitic. The latter can be developed as scaly spines, rows of blades, or comarginal, radial arched lamellae. We investigated biological crystal morphology and mode of assembly of Chama arcana and Chama gryphoides shells. Structural characteristics were obtained from electron backscatter diffraction (EBSD) measurements, complemented with laser confocal and BSE imaging. We found a wide range of crystal morphologies and sizes, ranging from irregularly shaped calcite and/or aragonite prisms to tiny and thin aragonite laths. We observed four different modes of crystal assembly patterns: 1. strongly interlocked dendritic calcite units forming the ornamentation blades; 2. aragonite laths arranged to lamellae forming the outer shell layer, the layer adjacent to the calcite; 3. aragonite laths arranged into blocks comprising inner shell layers or aragonitic ornamentations; and 4. shell portions consisting of aragonite prisms, structured in size and crystal orientation, at muscle attachment sites. These four different types of crystal arrangements were observed for the shells of the investigated chamid species; however, they had slightly different strengths of structuring and slight variations in crystal organisation. Additionally, we observed unique microstructural features in Chama shells: We report ornamentation crystals resembling idiomorphic calcite and novel, twinned entities found at the changeover between the aragonitic layers. We highlight and discuss these differences and anomalies in this contribution. Full article

(This article belongs to the Section Mineralogical Crystallography and Biomineralization)

► Show Figures

Figure 1

1 pages, 136 KiB

Open AccessRetraction

RETRACTED: Vasyliv et al. The Effect of Treatment Temperature on Microstructure and Mechanical Behavior of a Fine-Grained YSZ–NiO(Ni) Anode Material. Crystals 2023, 13, 944

by Bogdan Vasyliv, Volodymyr Kulyk, Zoia Duriagina and Taras Kovbasiuk

Crystals 2024, 14(7), 648; https://doi.org/10.3390/cryst14070648 - 15 Jul 2024

Viewed by 564

Abstract

The journal Crystals retracts the article titled, “The Effect of Treatment Temperature on Microstructure and Mechanical Behavior of a Fine-Grained YSZ–NiO(Ni) Anode Material” [...] Full article

19 pages, 10752 KiB

Open AccessReview

Synthesis, Characterisation, and Applications of TiO and Other Black Titania Nanostructures Species (Review)

by Simonas Ramanavicius and Arunas Jagminas

Crystals 2024, 14(7), 647; https://doi.org/10.3390/cryst14070647 - 14 Jul 2024

Cited by 4 | Viewed by 1220

Abstract

Black titania, a conductive ceramic material class, has garnered significant interest due to its unique optical and electrochemical properties. However, synthesising and properly characterising these structures pose a considerable challenge. This diverse material family comprises various titanium oxide phases, many of them non-stoichiometric. [...] Read more.

Black titania, a conductive ceramic material class, has garnered significant interest due to its unique optical and electrochemical properties. However, synthesising and properly characterising these structures pose a considerable challenge. This diverse material family comprises various titanium oxide phases, many of them non-stoichiometric. The term “black TiO₂” was first introduced in 2011 by Xiaobo Chen, but Arne Magneli’s groundbreaking discovery and in-depth investigation of black titania in 1957 laid the foundation for our understanding of this material. The non-stoichiometric black titanium oxides were then called the Magneli phases. Since then, the science of black titania has advanced, leading to numerous applications in photocatalysis, electrocatalysis, supercapacitor electrodes, batteries, gas sensors, fuel cells, and microwave absorption. Yet, the literature is rife with conflicting reports, primarily due to the inadequate analysis of black titania materials. This review aims to provide an overview of black titania nanostructures synthesis and the proper characterisation of the most common and applicable black titania phases. Full article

(This article belongs to the Special Issue Advances in Functional Inorganic Materials Prepared by Wet Chemical Methods (Third Edition))

► Show Figures

Figure 1

11 pages, 3629 KiB

Open AccessArticle

Thermal Behavior of Clinoptilolite

by Magdalena Król, Jakub Dechnik, Patryk Szymczak, Bartosz Handke, Magdalena Szumera and Paweł Stoch

Crystals 2024, 14(7), 646; https://doi.org/10.3390/cryst14070646 - 14 Jul 2024

Viewed by 1051

Abstract

Understanding the thermal properties of zeolites is crucial for their industrial applications. This study explores the thermal stability and dehydration process of clinoptilolite using high-temperature X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Clinoptilolite’s thermal decomposition was monitored from 25 °C to [...] Read more.

Understanding the thermal properties of zeolites is crucial for their industrial applications. This study explores the thermal stability and dehydration process of clinoptilolite using high-temperature X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Clinoptilolite’s thermal decomposition was monitored from 25 °C to 1200 °C, with results analyzed based on its crystal structure. Principal components analysis (PCA) of the DRIFT spectra indicated progressive water removal and dehydration upon heating, leading to the formation of hydrogen bonds. Thermogravimetric analysis (TGA) revealed a two-step endothermic weight loss: initially, physically adsorbed water was lost up to 100 °C, followed by the removal of tightly bound water and hydroxyl groups until 800 °C. Clinoptilolite remained the dominant phase up to 800 °C, after which albite and cristobalite took over. Rietveld refinement showed that the sample initially contained 70% clinoptilolite, 24% albite, and 6% cristobalite. Above 800 °C, clinoptilolite disappeared, leaving 93% albite and 7% cristobalite. FT-IR spectra changes due to water loss were evident: drying of adsorbed water occurred up to 75 °C and minimal changes were observed from 75 °C to 135 °C, followed by further dehydration until 240 °C. Complete dehydration was confirmed by the disappearance of OH stretching vibration bands by 395 °C, consistent with TGA findings. Full article

(This article belongs to the Section Hybrid and Composite Crystalline Materials)

► Show Figures

Figure 1

17 pages, 3995 KiB

Open AccessArticle

Density Functional Theory Calculations for Interpretation of Infra-Red Spectra of Liquid Crystalline Chiral Compound

by Aleksandra Deptuch, Natalia Górska, Michaela Murzyniec, Monika Srebro-Hooper, James Hooper, Magdalena Dziurka and Magdalena Urbańska

Crystals 2024, 14(7), 645; https://doi.org/10.3390/cryst14070645 - 13 Jul 2024

Viewed by 1155

Abstract

The experimental IR spectra of (S)-4′-(1-methylheptyloxycarbonyl) biphenyl-4-yl 4-[2-(2,2,3,3,4,4,4-heptafluorobutoxy) ethyl-1-oxy]-2-fluorobenzoate in the crystal phase are analyzed with the help of dispersion-corrected density functional theory (DFT+D3) calculations for isolated molecular monomer and dimer models, and a periodic model computed at the extended density [...] Read more.

The experimental IR spectra of (S)-4′-(1-methylheptyloxycarbonyl) biphenyl-4-yl 4-[2-(2,2,3,3,4,4,4-heptafluorobutoxy) ethyl-1-oxy]-2-fluorobenzoate in the crystal phase are analyzed with the help of dispersion-corrected density functional theory (DFT+D3) calculations for isolated molecular monomer and dimer models, and a periodic model computed at the extended density functional tight-binding (xTB) level of theory. It is found that the frequency scaling coefficients obtained with the results of the molecular calculations are good matches for the crystal phase, being close to 1. The molecular and periodic models both confirm that varied intra- and intermolecular interactions are crucial in order to reproduce the broadened shape of the experimental band related to C=O stretching; the key factors are the conjugation of the ester groups with the aromatic rings and the varied intermolecular chemical environments, wherein the C=O group that bridges the biphenyl and F-substituted phenyl groups seems particularly sensitive. The C=O stretching vibrations are investigated as a function of temperature, covering the range of the crystal, smectic C_A*, smectic C* and isotropic liquid phases. The structure changes are followed based on the X-ray diffraction patterns collected in the same temperatures as the IR spectra. The experimental and computational results taken together indicate that the amount of weak C=O…H-C hydrogen bonds between the molecules in the smectic layers decreases with increasing temperature. Full article

(This article belongs to the Special Issue Liquid Crystal Research and Novel Applications in the 21st Century)

► Show Figures

Figure 1

19 pages, 3750 KiB

Open AccessArticle

Visible-Light Spectroscopy and Rock Magnetic Analyses of Iron Oxides in Mixed-Mineral Assemblages

by Christopher J. Lepre, Owen M. Yazzie and Benjamin R. Klaus

Crystals 2024, 14(7), 644; https://doi.org/10.3390/cryst14070644 - 13 Jul 2024

Cited by 1 | Viewed by 890

Abstract

Iron oxide assemblages are central to many pursuits, ranging from Mars exploration to environmental remediation. Oxides and oxyhydroxides of iron both carry the special properties of color and magnetism. In this paper, we use visible-light spectroscopy and rock magnetic data collected at varying [...] Read more.

Iron oxide assemblages are central to many pursuits, ranging from Mars exploration to environmental remediation. Oxides and oxyhydroxides of iron both carry the special properties of color and magnetism. In this paper, we use visible-light spectroscopy and rock magnetic data collected at varying temperatures (~77–973 K) to analyze the concentrations and identities of iron oxides found in natural hematite-dominated samples that were obtained from a scientific drill core of Late Triassic red beds in the American Southwest. Our results suggest that hematite colorization of Earth materials varies from red to blue/purple as crystal size increases. Second-derivative analysis of the collected visible-light spectra allows this variation to be measured through the characteristic wavelength band position. Magnetic coercivity data indicate “hardness” differences that also may suggest smaller grain sizes are associated with redder colors. Yellowish maghemite and goethite have overlapping characteristic wavelength band positions that make it challenging to distinguish their contributions to mixed assemblages from visible-light data alone. Remanent magnetizations acquired at ~77 K and room temperature suggest the presence of hematite and a low-coercivity phase that may be maghemite and/or oxidized magnetite. However, we interpret this phase as maghemite in order to explain the changes in iron oxide concentrations indicated by visible-light intensities near ~425 nm and because the thermal demagnetization data suggest that goethite is absent from the samples. Future research that increases the resolution of hematite, maghemite, and goethite detection in experimental and natural samples will provide opportunities to refine the study of past climates and constrain soil iron availability under future changes in global moisture and temperature. Multimethod datasets improve understanding of environmental conditions that cause iron oxides assemblages to shift in phase dominance, grain size, and crystallinity. Full article

(This article belongs to the Special Issue Metal Oxides: Crystal Structure, Synthesis and Characterization)

► Show Figures

Figure 1

18 pages, 15908 KiB

Open AccessArticle

The Influence of Process Parameters on the Microstructure and Microhardness of 304 Stainless Steel in Joule Heating Fused Filament Fabrication

by Suli Li, Jichao Chen, Longfei Fan, Jie Xiong, Zhuang Gao and Laixia Yang

Crystals 2024, 14(7), 643; https://doi.org/10.3390/cryst14070643 - 12 Jul 2024

Viewed by 627

Abstract

Using finite element simulation and single-variable experimental methods, this study analyzes the variations in the microstructure and hardness of a 304 stainless steel wire during Joule heating fused filament fabrication. The effects of current intensity, printing speed, and roller pressure on the macroscopic [...] Read more.

Using finite element simulation and single-variable experimental methods, this study analyzes the variations in the microstructure and hardness of a 304 stainless steel wire during Joule heating fused filament fabrication. The effects of current intensity, printing speed, and roller pressure on the macroscopic morphology, microstructure, and microhardness of a single-layer single-channel formation were investigated. The results indicate that when the current intensity is 400 A, the printing speed is 1000 mm/min, and the roller pressure is 0.3 N, the surface of the single-layer single-channel formation is smooth and exhibits optimal forming characteristics with a width-to-height ratio of 3.23, a dilution rate of 51.61%, and an average microhardness of 238.17 HV. As the current intensity increases, the microstructure in the fusion zone initially decreases in size and then increases; similarly, with the increase in printing speed, the microstructure in the fusion zone first decreases and then increases; as the roller pressure increases, the microstructure in the fusion zone initially increases in size and then decreases. The microhardness initially increases and then decreases with the increase in process parameters, resulting in uneven hardness distribution due to the variations in microstructure size. The optimal combination of process parameters achieves a balance between heat input, cooling rate, and growth rate, thereby achieving grain refinement and hardness improvement, ultimately enhancing the mechanical properties of the material. Full article

(This article belongs to the Special Issue Advances in Microstructure and Plastic Deformation of High-Strength Steels)

► Show Figures

Figure 1

17 pages, 4144 KiB

Open AccessArticle

Study of the Influence of the Change from Methyl to Isopropyl Substituents in 1-(2,4,6-trialkylphenyl)ethanol on the Point Group Symmetry of the 0-D Hydrogen-Bonded Moiety

by Ewa M. Iwanek (nee Wilczkowska) and Marek Gliński

Crystals 2024, 14(7), 642; https://doi.org/10.3390/cryst14070642 - 12 Jul 2024

Cited by 1 | Viewed by 680

Abstract

The steric hindrance in molecules of 1-(2,4,6-trimethylphenyl)ethanone and 1-(2,4,6-triisopropylphenyl)ethanone were shown to substantially differentiate the options of synthesis of the respective alcohols. The former was obtained with a yield of 12% with a mild reducing agent, i.e., NaBH₄, as well as [...] Read more.

The steric hindrance in molecules of 1-(2,4,6-trimethylphenyl)ethanone and 1-(2,4,6-triisopropylphenyl)ethanone were shown to substantially differentiate the options of synthesis of the respective alcohols. The former was obtained with a yield of 12% with a mild reducing agent, i.e., NaBH₄, as well as in vapor phase transfer hydrogenation (22% yield at 673 K) over MgO, whereas the latter was not formed at all under those conditions. The only agent that was able to reduce both ketones was LiAlH₄. The single crystals of the two alcohols were obtained and their structures were determined. The symmetry of the 0-D hydrogen-bonded networks of molecules in these crystals was analyzed. It was shown that the methyl substituent allows the molecules to form hexameric rings, whereas the isopropyl-substituted molecules formed tetrameric ones. In both cases, there were two types of rings in the cell, but four types of molecules forming tetramers and only three types of molecules in the hexamers. These structures were compared to similar structures formed by other molecules found in the Cambridge Structural Database via hydrogen bonding. Moreover, the single crystal of 1-(2,4,6-triisopropylphenyl)ethanone was obtained to explain if either the hydrogen bonding or the presence of isopropyl groups influences the angles in the molecules. Full article

(This article belongs to the Section Organic Crystalline Materials)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Crystals, Volume 14, Issue 7 (July 2024) – 95 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI