Search Results (35)

This paper presents a novel low-carbon binder formulated from fly ash (FA), ground granulated blast furnace slag, steel slag, and desulfurization gypsum as a quaternary solid waste-based material. It specifically examines the influence of FA content on the mechanical properties and hydration reactions of the quaternary solid waste-based binder. The mortar test results indicate that the optimal FA content is 10%, which yields a 28-day compressive strength 11.28% higher than that of the control group without FA. The spherical particles of fly ash reduce the overall water demand and provide a “lubricating” effect to the paste due to their continuous gradation, improving the fluidity of the slag-steel slag-gypsum cementitious materials. The micro test results indicate that fly ash has minimal effect on the early hydration products and process of the solid waste-based cementitious materials, but after 7 days, it continuously dissolves silicon-oxygen tetrahedrons or aluminum-oxygen tetrahedrons, consuming Ca²⁺ and OH⁻ in the system. After 28 days, the amount of ettringite and C-(A)-S-H gel generated increases significantly. The pozzolanic activity of fly ash is mainly stimulated by the Ca(OH)₂ from steel slag in the later hydration stage. Additionally, spherical fly ash particles can fill the voids in the hardened paste, reducing the formation of cracks and weak zones, and thereby contributing to a denser overall structure of the hydrated binder. The findings of this paper provide data support for the development of low-carbon cement-free binders using fly ash in conjunction with metallurgical slags, thereby contributing to the low-carbon advancement of the construction materials industry. Full article

The thermal expansion of four alkaline-earth borates, namely Ca₃B₂O₆ (0D), CaB₂O₄ (1D), Sr₃B₁₄O₂₄ (2D) and CaB₄O₇ (3D), has been studied by in situ high-temperature powder X-ray diffraction (HTXRD). Strong anisotropy of thermal expansion is observed for the structures of Ca₃B₂O₆ (0D) and CaB₂O₄ (1D) built up from BO₃ triangles only; these borates exhibit maximal expansion perpendicular to the BO₃ plane, i.e., along the direction of weaker bonding in the crystal structure. Layered Sr₃B₁₄O₂₄ (2D) and framework CaB₄O₇ (3D) built up from various B–O groups expand less anisotropically. The thermal properties of the studied compounds compared to the other alkaline-earth borates are summarized depending on the selected structural characteristics like anion dimensionality, residual charge per one polyhedron (BO₃ BO₄), cationic size and charge, and structural complexity. For the first time, these dependencies are established as an average for both types of polyhedra (triangle and tetrahedron) occurring in the same structure at the same time. The most common trends identified from these studies are as follows: (i) melting temperature decreases with the dimensionality of the borate polyanion, and more precisely, as the residual charge per one polyhedron (triangle or tetrahedron) decreases; (ii) volumetric expansion decreases while the degree of anisotropy increases weakly when the residual charge decreases; (iii) both trends (i) and (ii) are most steady within borates built by triangles only, while borates built by both triangles and tetrahedra show more scattered values. Full article

This paper is part of a series that describes the Fibonacci icosagrid quasicrystal (FIG) and its relation to the $E_8$ root lattice. The FIG was originally constructed to represent the intersection points of an icosahedrally symmetric collection of planar grids in three dimensions, with the grid spacing of each following a Fibonacci chain. It was found to be closely related to a five-fold compound of 3D sections taken from the 4D Elser–Sloane quasicrystal (ESQC), which is derived via a cut-and-project process from $E_8$. More recently, a direct cut-and-project from $E_8$ has been found which yields the FIG (presented in another paper of this series). The present paper focuses not on the full quasicrystal, but on the relationship between the root polytope of $E_8$ (Gosset’s $4_{21}$ polytope) and the core polyhedron generated in the FIG, a compound of 20 tetrahedra referred to simply as a 20-Group. In particular, the $H_3$ symmetry of the FIG can be seen as a five-fold or “golden” composition of tetrahedral symmetry (referring to the characteristic appearance of the golden ratio). This is shown to mirror a connection between tetrahedral and five-fold symmetries present in the $4_{21}$. Indeed, the rotations that connect tetrahedra contained within the $4_{21}$ are shown to induce, in a certain natural way, the tetrahedron orientations in the 20-Group. Full article

The [Ag(3ADMT)(NO₃)]_n complex was synthesized by the self-assembly of 3-amino-5,6-dimethyl-1,2,4-triazine (3ADMT) and AgNO₃. Its molecular structure was analyzed utilizing FTIR spectra, elemental analysis, and single crystal X-ray diffraction (SC-XRD). There is one crystallographically independent Ag atom, which is tetra-coordinated by two nitrogen atoms from two 3ADMT and two oxygen atoms from two nitrate anions where all ligand groups are acting as connectors between the Ag1 sites. The geometry around the Ag(I) center is a distorted tetrahedron with a AgN₂O₂ coordination sphere augmented by strong argentophilic interactions between Ag atoms, which assist the aggregation of the complex units in a wavy-like and coplanar pattern to form a one-dimensional polymeric chain. The O...H (37.2%) and N...H (18.8%) intermolecular interactions contributed significantly to the molecular packing based on Hirshfeld surface analysis. The [Ag(3ADMT)(NO₃)]_n complex demonstrates promising cytotoxicity against lung (IC₅₀ = 2.96 ± 0.31 μg/mL) and breast (IC₅₀ = 1.97 ± 0.18 μg/mL) carcinoma. This remarkable cytotoxicity exceeds those of 3ADMT, AgNO₃, and the anticancer medication cis-platin towards the tested cancer cell lines. In addition, the complex has a wide-spectrum antimicrobial action where the high antibacterial potency of the [Ag(3ADMT)(NO₃)]_n complex against P. vulgaris (MIC = 6.1 µg/mL) and B. subtilis (MIC = 17.2 µg/mL) could be comparable to the commonly used drug Gentamycin (MIC = 4.8 µg/mL). These results confirm that the components of the [Ag(3ADMT)(NO₃)]_n complex work together synergistically, forming a powerful multifunctional agent that could be exploited as an effective antimicrobial and anticancer agent. Full article

The crystal structure of manganotychite has been refined using the holotype specimen from the Alluaiv Mountain, Lovozero massif, Kola peninsula, Russia. The mineral is cubic, Fd$\overline{3}$, a = 14.0015(3) Å, V = 2744.88(18) ų, Z = 8, R₁ = 0.020 for 388 independently observed reflections. Manganotychite is isotypic to tychite and ferrotychite. Its crystal structure is based upon a three-dimensional infinite framework formed by condensation of MnO₆ octahedra and CO₃ groups by sharing common O atoms. The sulfate groups and Na⁺ cations reside in the cavities of the octahedral-triangular metal-carbonate framework. In terms of symmetry and basic construction of the octahedral-triangular framework, the crystal structure of manganotychite is identical to that of northupite, Na₃Mg(CO₃)₂Cl. The transition northupite → tychite can be described as a result of the multiatomic 2Cl⁻ → (SO₄)²⁻ substitution, where both chlorine and sulfate ions are the extra-framework constituents. However, the positions occupied by sulfate groups and chlorine ions correspond to different octahedral cavities within the skeletons of Na atoms. The crystal structure of northupite can be considered as an interpenetration of two frameworks: anionic [Mg(CO₃)₂]²⁻ octahedral-triangular framework and cationic [ClNa₃]²⁻ framework with the antipyrochlore topology. Both manganotychite and northupite structure types can be described as a modification of the crystal structure of diamond (or the dia net) via the following steps: (i) replacement of a vertex of the dia net by an M₄ tetrahedron (no symmetry reduction); (ii) attachment of (CO₃) triangles to the triangular faces of the M₄ tetrahedra (accompanied by the Fd$\overline{3}$m → Fd$\overline{3}$ symmetry reduction); (iii) filling voids of the resulting framework by Na⁺ cations (no symmetry reduction); and (iv) filling voids of the Na skeleton by either sulfate groups (in tychite-type structures) or chlorine atoms (in northupite). As a result, the information-based structural complexity of manganotychite and northupite exceeds that of the dia net. Full article

Energy-relevant small molecule activations and related processes are often multi-electron in nature. Ferrocene is iconic for its well-behaved one-electron chemistry, and it is often used to impart redox activity to self-assembled architectures. When multiple ferrocenes are present as pendant groups in a single structure, they often behave as isolated sites with no separation of their redox events. Herein, we study a suite of molecules culminating in a self-assembled palladium(II) truncated tetrahedron (TT) with six pendant ferrocene moieties using the iron(III/II) couple to inform about the electronic structure and, in some cases, subsequent reactivity. Notably, although known ferrocene-containing metallacycles and cages show simple reversible redox chemistry, this TT undergoes a complex multi-step electrochemical mechanism upon oxidation. The electrochemical behavior was observed by voltammetric and spectroelectrochemical techniques and suggests that the initial Fc-centered oxidation is coupled to a subsequent change in species solubility and deposition of a film onto the working electrode, which is followed by a second separable electrochemical oxidation event. The complicated electrochemical behavior of this self-assembly reveals emergent properties resulting from organizing multiple ferrocene subunits into a discrete structure. We anticipate that such structures may provide the basis for multiple charge separation events to drive important processes related to energy capture, storage, and use, especially as the electronic communication between sites is further tuned. Full article

Cholic acid is a trihydroxy bile acid with a nice peculiarity: the average distance between the oxygen atoms (O7 and O12) of the hydroxy groups located at C7 and C12 carbon atoms is 4.5 Å, a value which perfectly matches with the O/O tetrahedral edge distance in Ih ice. In the solid phase, they are involved in the formation of hydrogen bonds with other cholic acid units and solvents. This fact was satisfactorily used for designing a cholic dimer which encapsulates one single water molecule between two cholic residues, its oxygen atom (Ow) being exactly located at the centroid of a distorted tetrahedron formed by the four steroid hydroxy groups. The water molecule participates in four hydrogen bonds, with the water simultaneously being an acceptor from the 2 O12 (hydrogen lengths are 2.177 Å and 2.114 Å) and a donor towards the 2 O7 (hydrogen bond lengths are 1.866 Å and 1.920 Å). These facts suggest that this system can be a nice model for the theoretical study of the formation of ice-like structures. These are frequently proposed to describe the water structure found in a plethora of systems (water interfaces, metal complexes, solubilized hydrophobic species, proteins, and confined carbon nanotubes). The above tetrahedral structure is proposed as a reference model for those systems, and the results obtained from the application of the atoms in molecules theory are presented here. Furthermore, the structure of the whole system allows a division into two interesting subsystems in which water is the acceptor of one hydrogen bond and the donor of another. The analysis of the calculated electron density is performed through its gradient vector and the Laplacian. The calculation of the complexation energy used correction of the basis set superposition error (BSSE) with the counterpoise method. As expected, four critical points located in the H…O bond paths were identified. All calculated parameters obey the proposed criteria for hydrogen bonds. The total energy for the interaction in the tetrahedral structure is 54.29 kJ/mol, while the summation obtained of the two independent subsystems and the one between the alkyl rings without water is only 2.5 kJ/mol higher. This concordance, together with the calculated values for the electron density, the Laplacian of the electron density, and the lengths of the oxygen atom and the hydrogen atom (involved in the formation of each hydrogen bond) to the hydrogen bond critical point, suggests that each pair of hydrogen bonds can be considered independent of each other. Full article

Aimed at improving the production efficiency of tetrahedron-like pervious frames for the river revetment, self-compacting steel fiber reinforced concrete (SFRC) was applied to strengthen the tensile resistance of concrete to remove conventional steel bars used as reinforcement. The workability and mechanical properties of self-compacting SFRC were experimentally studied with the volume fraction of steel fiber changed from 0.4% to 1.2%, and the rational volume fraction of 0.8% was determined for producing the pervious frames. Based on the flow-induced orientation of the steel fibers in the fresh mix, the casting process of self-compacting SFRC was optimal from one inclined rod to other two inclined rods and the horizontal rods of the pervious frame. The loading capacities of pervious frames during lifting and stacking were respectively detected by the simulation tests on the testing machine, which ensure the safety of pervious frames lifted six layers together and stacked for nineteen layers. By testing groups of pervious frames throwed in and then salvaged from the river, the quality of pervious frames without any damage was observed. Finally, the pervious frames were successfully applied in an engineering project for the river revetment. Full article

We have previously published on a new triazolic phosphonic α-amino ester in position 4 on the triazole ring of a naphthalene ester. The aim of the present paper was to describe its crystallographic study by XRD. The crystal structure of naphthalen-2-yl 1-(benzamido(diethoxyphosphoryl)methyl)-1H-1,2,3-triazole-4-carboxylate was determined by single-crystal X-ray diffraction. This compound crystallizes in the monoclinic system, space group P2₁/c. The naphthalene system is almost planar and makes dihedral angles of 67.1(2)° and 63.9(2)° with the triazole ring and the phenyl cycle, respectively. The phosphorus atom is surrounded by three oxygen atoms and one carbon atom building a distorted tetrahedron. It is also noted, that one of the two ethyl groups is disordered. In the crystal, the molecules are connected through C-H…O and N-H…O hydrogen bonds to build dimers that are linked together by C-H…O hydrogen bonds, in addition to C-H…π interactions. The presence of an intramolecular hydrogen bond contributes to the stability of the molecular conformation by completing the S(5) cycle. Full article

The main aim of this paper is to study the cation fixation sites in montmorillonite after heating at different temperatures. Montmorillonite was used to adsorb cations (Na⁺, Cu²⁺ and Li⁺) in the solution, and the montmorillonite-adsorbed cations were heated at different temperatures (unheated, 100 °C, 200 °C and 300 °C) for 25 h. Subsequently, the basal spacing of montmorillonite treated at different temperatures was monitored by X-ray diffraction (XRD). The exchangeable cationic content (Na⁺, Cu²⁺ and Li⁺) in montmorillonite was determined based on an inductively coupled plasma emission spectrometer (ICP-OES). In addition, the stretching and bending vibration changes in the OH group and the Si-O bond in montmorillonite were detected by Fourier transform infrared spectroscopy (FTIR). The vibration changes were related to the cation fixation sites. The XRD data showed that when the heating temperature reached 200 °C, the structure of montmorillonite adsorbing Li⁺ and Cu²⁺ ions completely collapsed, but the layer spacing of montmorillonite adsorbing Na⁺ decreased slightly, which indicated that Li⁺ and Cu²⁺ were more easily able to enter the crystal structure. The ICP-OES results showed that the contents of exchangeable Na⁺, Cu²⁺ and Li⁺ in montmorillonite decreased with the increase in heating temperature, and Li⁺ was more easily fixed by montmorillonite than Na⁺ and Cu²⁺. The FTIR data showed that when montmorillonite adsorbed with Li⁺ was heated at more than 200 °C, a new OH stretching vibration band appeared at 3971 cm⁻¹, which may be caused by the migration of Li⁺ into the octahedral vacancy to form a local trioctahedral structure. Na⁺ has a large radius; it can only be fixed near the OH group and may not enter the tetrahedron/octahedron of montmorillonite. The number of charges carried by Cu²⁺ is high and the dehydration enthalpy of hydrated Cu²⁺ is high. When the heating temperature was greater than 200 °C, Cu²⁺ mainly entered the hexagonal cavity of the tetrahedron and caused slight changes in the OH bending vibration. The vibration of the Si-O bond hardly changed after montmorillonite adsorbed Na⁺, but the stretching vibration peak of the Si-O bond moved to the high value region after adsorbing Cu²⁺ and Li⁺, which was speculated to be related to the migration of Cu²⁺ and Li⁺ into the crystal structure. Full article

Kenoargentotetrahedrite-(Fe) is observed as greenish-grey anhedral grains, 50–150 μm in size, in association with galena, sphalerite and chalcopyrite in the Bajiazi Pb-Zn deposit of magmatic-hydrothermal type, Liaoning, China. The empirical formula from electron microprobe analyses is Ag_5.50Cu_4.17Fe_1.75Zn_0.31Sb_3.96As_0.04S_12.08, corresponding to the ideal formula Ag₆Cu₄Fe₂Sb₄S₁₂. The crystal structure of kenoargentotetrahedrite-(Fe) has been determined and refined by single-crystal X-ray diffraction with R₁ = 0.0192 for 1866 (404 unique) reflections. It is cubic, space group I$\overline{4}$3m with unit cell parameters a = 10.4928(2) Å, V = 1155.26(7) ų and Z = 2. The structure of kenoargentotetrahedrite-(Fe) is characterized by a poor occupancy of 0.05 of the octahedral S(2) site with the S(2)-M(2) bonding length of 1.9994(8) Å. The six Ag atoms at M(2) around S(2) form an octahedron cluster (Ag₆)⁴⁺ with the valence state of +4 and Ag-Ag distance of 2.8276(1) Å. The structure is identical to that by Rozhdestvenskaya et al., being composed of a collapsed sodalite-like framework of corner-connected M(1)S₄ tetrahedron forming cages containing M(2)₆-octahedron cluster, encircled by four SbS₃ trigonal pyramids. It is related to the tetrahedrite group minerals with the existence of the (Ag₆)⁴⁺ cluster replacing the S(2)-centered Ag₆ octahedron according to the substitution mechanism 6^M(2)Ag⁺ + ^S(2)S²⁻=^M(2)(Ag₆)⁴⁺ + ^S(2) S. Full article

In this paper, we report on the chemical preparation, crystal details, vibrational, optical, and thermal behavior, and antibacterial activity of a new non-centrosymmetric compound: 4-tert-butyl-pyridinium tetrachloridocuprate. X-ray diffraction analysis shows that the structure has a 3D network made up of C–H…Cl and N–H…Cl H-bonds, and [CuCl₄]²⁻ anions have a shape halfway between a tetrahedron and a square planar structure in this compound’s monoclinic system. Hirshfeld surface analysis was used to explain the nature and extent of intermolecular interactions, highlighting the importance of the H-bonds and the C–H⋯π interactions in the structure’s stabilization. Additionally, SEM/EDX experiments were conducted. The powder X-ray diffraction investigation at room temperature validated the material purity. Moreover, the different functional groups were identified using FT-IR spectroscopy. In addition, the optical properties were investigated using UV-Vis absorption. The thermal stability of (C₉H₁₄N)₂[CuCl₄] was performed by TGA-DTA. The bactericidal potency of the title compound was surveyed. Full article

Additive manufacturing technologies have a lot of potential advantages for construction application, including increasing geometrical construction flexibility, reducing labor costs, and improving efficiency and safety, and they are in line with the sustainable development policy. However, the full exploitation of additive manufacturing technology for ceramic materials is currently limited. A promising solution in these ranges seems to be geopolymers reinforced by short fibers, but their application requires a better understanding of the behavior of this group of materials. The main objective of the article is to investigate the influence of the microstructure of the material on the mechanical properties of the two types of geopolymer composites (flax and carbon-reinforced) and to compare two methods of production of geopolymer composites (casting and 3D printing). As raw material for the matrix, fly ash from the Skawina coal power plant (located at: Skawina, Lesser Poland, Poland) was used. The provided research includes mechanical properties, microstructure investigations with the use of scanning electron microscope (SEM), confocal microscopy, and atomic force microscope (AFM), chemical and mineralogical (XRD-X-ray diffraction, and XRF-X-ray fluorescence), analysis of bonding in the materials (FT-IR), and nuclear magnetic resonance spectroscopy analysis (NMR). The best mechanical properties were reached for the sample made by simulating 3D printing process for the composite reinforced by flax fibers (48.7 MPa for the compressive strength and 9.4 MPa for flexural strength). The FT-IR, XRF and XRD results show similar composition of all investigated materials. NMR confirms the presence of SiO₄ and AlO₄ tetrahedrons in a three-dimensional structure that is crucial for geopolymer structure. The microscopy observations show a better coherence of the geopolymer made in additive technology to the reinforcement and equal fiber distribution for all investigated materials. The results show the samples made by the additive technology had comparable, or better, properties with those made by a traditional casting method. Full article

In this work, for the first time, the influence of the coordination environment as well as Ca and P atomic states on biomimetic composites integrated with dental tissue was investigated. Bioinspired dental composites were synthesised based on nanocrystalline calcium carbonate-substituted hydroxyapatite $C{a}_4^{\mathrm{I}}C{a}_6^{\mathrm{II}}{\left(P{O}_4\right)}_{6-x}{\left(C{O}_3\right)}_{x+y}{\left(OH\right)}_{2-y}$ (nano-cHAp) obtained from a biogenic source and a set of polar amino acids that modelled the organic matrix. Biomimetic composites, as well as natural dental tissue samples, were investigated using Raman spectromicroscopy and synchrotron X-ray absorption near edge structure (XANES) spectroscopy. Molecular structure and energy structure studies revealed several important features related to the different calcium atomic environments. It was shown that biomimetic composites created in order to reproduce the physicochemical properties of dental tissue provide good imitation of molecular and electron energetic properties, including the carbonate anion CO₃²⁻ and the atomic Ca/P ratio in nanocrystals. The features of the molecular structure of biomimetic composites are inherited from the nano-cHAp (to a greater extent) and the amino acid cocktail used for their creation, and are caused by the ratio between the mineral and organic components, which is similar to the composition of natural enamel and dentine. In this case, violation of the nano-cHAp stoichiometry, which is the mineral basis of the natural and bioinspired composites, as well as the inclusion of different molecular groups in the nano-cHAp lattice, do not affect the coordination environment of phosphorus atoms. The differences observed in the molecular and electron energetic structures of the natural enamel and dentine and the imitation of their properties by biomimetic materials are caused by rearrangement in the local environment of the calcium atoms in the HAp crystal lattice. The surface of the nano-cHAp crystals in the natural enamel and dentine involved in the formation of bonds with the organic matrix is characterised by the coordination environment of the calcium atom, corresponding to its location in the Ca^I position—that is, bound through common oxygen atoms with PO₄ tetrahedrons. At the same time, on the surface of nano-cHAp crystals in bioinspired dental materials, the calcium atom is characteristically located in the Ca^II position, bound to the hydroxyl OH group. The features detected in the atomic and molecular coordination environment in nano-cHAp play a fundamental role in recreating a biomimetic dental composite of the natural organomineral interaction in mineralised tissue and will help to find an optimal way to integrate the dental biocomposite with natural tissue. Full article

The symmetry SU(2) and its geometric Bloch Sphere rendering have been successfully applied to the study of a single qubit (spin-1/2); however, the extension of such symmetries and geometries to multiple qubits—even just two—has been investigated far less, despite the centrality of such systems for quantum information processes. In the last two decades, two different approaches, with independent starting points and motivations, have been combined for this purpose. One approach has been to develop the unitary time evolution of two or more qubits in order to study quantum correlations; by exploiting the relevant Lie algebras and, especially, sub-algebras of the Hamiltonians involved, researchers have arrived at connections to finite projective geometries and combinatorial designs. Independently, geometers, by studying projective ring lines and associated finite geometries, have come to parallel conclusions. This review brings together the Lie-algebraic/group-representation perspective of quantum physics and the geometric–algebraic one, as well as their connections to complex quaternions. Altogether, this may be seen as further development of Felix Klein’s Erlangen Program for symmetries and geometries. In particular, the fifteen generators of the continuous SU(4) Lie group for two qubits can be placed in one-to-one correspondence with finite projective geometries, combinatorial Steiner designs, and finite quaternionic groups. The very different perspectives that we consider may provide further insight into quantum information problems. Extensions are considered for multiple qubits, as well as higher-spin or higher-dimensional qudits. Full article