Theoretical and X-ray studies on the cyclisation of 1-phenyl-5-(3-aryltriaz-1-en-1-yl)-1Hpyrazole- 4-carbonitriles and 2-amino-3-(3-aryltriaz-1-en-1-yl)maleonitriles: A comparison study

The present work investigates attempts to cyclise 1-phenyl-5-(3-aryltriaz-1-en-1-yl)-1H-pyrazole- 4-carbonitriles to the desired pyrazolo[3,4-d][1,2,3]triazinimine derivatives. The cyclisations were unfruitful, and a density functional theory study was performed. This revealed the 1-phenyl-5-(3-aryltriaz-1-en-1-yl)-1H-pyrazole-4-carbonitriles are more stable than the targeted pyrazolo[3,4-d][1,2,3]triazinimine derivatives, indicating that their cyclisation is thermodynamically disfavoured; the reactant 8c is more stable than the predicted six-membered ring products 9c by 5 kJ/mol. The effect of isomerisation of the methoxy-phenyl group in the self-assembly of 8c and 8d in the crystalline lattice was investigated. The intermolecular forces in solid state were analysed in the two structural isomers 8c and 8d using calculated HirshFeld surface; the analysis indicates that the intermolecular forces are stronger in 8c than 8d and hence 8c is denser than 8d by 0.071g/mL.

Coherent spin rotation-induced zero thermal expansion in MnCoSi-based spiral magnets

Materials exhibiting zero thermal expansion (ZTE), namely, volume invariance with temperature change, can resist thermal shock and are highly desired in modern industries for high-precision components. However, pure ZTE materials are rare, especially those that are metallic. Here, we report the discovery of a pure metallic ZTE material: an orthorhombic Mn1-xNixCoSi spiral magnet. The introduction of Ni can efficiently enhance the ferromagnetic exchange interaction and construct the transition from a spiral magnetic state to a ferromagnetic-like state in MnCoSi-based alloys. Systematic in situ neutron powder diffraction revealed a new cycloidal spiral magnetic structure in the bc plane in the ground state, which transformed to a helical spiral in the ab plane with increasing temperature. Combined with Lorentz transmission electron microscopy techniques, the cycloidal and helical spin order coherently rotated at varying periods along the c-axis during the magnetic transition. This spin rotation drove the continuous movement of the coupled crystalline lattice and induced a large negative thermal expansion along the a-axis, eventually leading to a wide-temperature ZTE effect. Our work not only introduces a new ZTE alloy but also presents a new mechanism by which to discover or design ZTE magnets.

Effects of Oxide Additives on the Phase Structures and Electrical Properties of SrBi4Ti4O15 High-Temperature Piezoelectric Ceramics

In this work, SrBi4Ti4O15 (SBT) high-temperature piezoelectric ceramics with the addition of different oxides (Gd2O3, CeO2, MnO2 and Cr2O3) were fabricated by a conventional solid-state reaction route. The effects of oxide additives on the phase structures and electrical properties of the SBT ceramics were investigated. Firstly, X-ray diffraction analysis revealed that all these oxides-modified SBT ceramics prepared presented a single SrBi4Ti4O15 phase with orthorhombic symmetry and space group of Bb21m, the change in cell parameters indicated that these oxide additives had diffused into the crystalline lattice of SBT and formed solid solutions with it. The SBT ceramics with the addition of MnO2 achieved a high relative density of up to 97%. The temperature dependence of dielectric constant showed that the addition of Gd2O3 could increase the TC of SBT. At a low frequency of 100 Hz, those dielectric loss peaks appearing around 500 °C were attributed to the space-charge relaxation as an extrinsic dielectric response. The synergetic doping of CeO2 and Cr2O3 could reduce the space-charge-induced dielectric relaxation of SBT. The piezoelectricity measurement and electro-mechanical resonance analysis found that Cr2O3 can significantly enhance both d33 and kp of SBT, and produce a higher phase-angle maximum at resonance. Such an enhanced piezoelectricity was attributed to the further increased orthorhombic distortion after Ti4+ at B-site was substituted by Cr3+. Among these compositions, Sr0.92Gd0.053Bi4Ti4O15 + 0.2 wt% Cr2O3 (SGBT-Cr) presented the best electrical properties including TC = 555 °C, tan δ = 0.4%, kp = 6.35% and d33 = 28 pC/N, as well as a good thermally-stable piezoelectricity that the value of d33 was decreased by only 3.6% after being annealed at 500 °C for 4 h. Such advantages provided this material with potential applications in the high-stability piezoelectric sensors operated below 500 °C.

Methyl β-lactoside [methyl β-D-galactopyranosyl-(1→4)-β-D-glucopyranoside] monohydrate: a solvomorphism study

Methyl β-lactoside [methyl β-D-galactopyranosyl-(1→4)-β-D-glucopyranoside] monohydrate, C13H24O11·H2O, (I), was obtained via spontaneous transformation of methyl β-lactoside methanol solvate, (II), during air-drying. Cremer–Pople puckering parameters indicate that the β-D-Galp (β-D-galactopyranosyl) and β-D-Glcp (β-D-glucopyranosyl) rings in (I) adopt slightly distorted 4 C 1 chair conformations, with the former distorted towards a boat form (B C1,C4) and the latter towards a twist-boat form (O5 S C2). Puckering parameters for (I) and (II) indicate that the conformation of the βGalp ring is slightly more affected than the βGlcp ring by the solvomorphism. Conformations of the terminal O-glycosidic linkages in (I) and (II) are virtually identical, whereas those of the internal O-glycosidic linkage show torsion-angle changes of 6° in both C—O bonds. The exocyclic hydroxymethyl group in the βGalp residue adopts a gt conformation (C4′ anti to O6′) in both (I) and (II), whereas that in the βGlcp residue adopts a gg (gauche–gauche) conformation (H5 anti to O6) in (II) and a gt (gauche–trans) conformation (C4 anti to O6) in (I). The latter conformational change is critical to the solvomorphism in that it allows water to participate in three hydrogen bonds in (I) as opposed to only two hydrogen bonds in (II), potentially producing a more energetically stable structure for (I) than for (II). Visual inspection of the crystalline lattice of (II) reveals channels in which methanol solvent resides and through which solvent might exchange during solvomorphism. These channels are less apparent in the crystalline lattice of (I).

Terahertz Time-domain Spectroscopy as a Novel Tool for Crystallographic Analysis in Cellulose: Cellulose I to Cellulose Ii, Tracing the Structural Changes Under Chemical Treatment

Terahertz time-domain spectroscopy (THz-TDS) has expanded possibilities in cellulose crystallography research, as THz radiation detects most intermolecular vibrations and responds to the phonons of crystalline lattices. In this study, we traced the transformation of the cellulose crystalline lattice from cellulose I to cellulose II by THz-TDS and X-ray powder diffraction. Cellulose II was obtained by treating cellulose I with NaOH of different concentrations (0 wt%–20 wt%, at 2 wt% intervals). The THz absorption coefficient spectra of cellulose II showed three characteristic peaks (at 1.32 THz, 1.76 THz, and 2.77 THz). The THz absorption coefficient spectra of cellulose II treated with 20-wt% NaOH and cellulose I without NaOH treatment were fitted by a seventh-order Fourier series. Thus, the THz absorption coefficient spectra of samples treated with NaOH of other concentrations could be considered a combination of these two fitted profiles of cellulose I and cellulose II, multiplied by different coefficients. Furthermore, the coefficients could reflect the relative contents of cellulose I and cellulose II in the samples.

The basics of radiation damage in crystalline silicon networks by NIEL

Basically, radiation can cause two effects on materials: ionization and non-ionization. This work presented the theory involved in defects caused by non-ionization, known as NIEL, with a focus on silicon materials. When energy is transferred directly to the atoms in the crystalline lattice, it can either be dissipated in the form of vibrations or be large enough to pull atoms out of that lattice. This weakens the lattice, causing measurement errors that can lead to permanent damage. This study is extremely important because silicon materials are used in radiation detectors. These detectors cannot return false measurements, especially in dangerous situations, such as in nuclear reactor monitoring. After presenting the theory involved, examples are shown. Failures of up to 30% were found by the researchers.

Nonlinear Quantum Phenomena During the Polarization of Nanometer Layers of Proton Semiconductors and Dielectrics

This paper investigates the influence of the structure and parameters of the degenerate quasi-discrete energy spectrum of relaxers (protons) on the mechanism of nonlinear quantum diffusion polarization in nanoscale layers of hydrogen bonded crystals (HBC) in a wide range of parameters of fields (100 kV/m - 1000 MV/m) and temperatures (0-1550 K). The temperature dependence of the quantum transparency of the parabolic potential barrier for protons in HBC is calculated using the Gibbs quantum canonical distribution for the ensemble of non-interacting protons (ideal proton gas balanced with the ions of anion sub-lattice) moving in an onedimensional potential field of a crystalline lattice (in the field of hydrogen bonds) with a zone structure distributed by energy levels. The influence of "zero" oscillations of protons on the temperature dependences of the proton subsystem kinetic coefficients in HBC is considered. It is revealed that proton tunneling influences the nonlinear space-charge polarization kinetics in HBC at high (150-550 K) and ultrahigh (550-1550 K) temperatures when crystalline layer thickness ranges from 1 to 10 nm. The results of theoretical studies (based on earlier experiments) are bound to be prospective for the prediction of HBC-class (KDP, DKDP) ferroelectrics properties, studying the second-order nonlinear optical effects of femtosecond lasers, and the development of memory cells for non-volatile high-speed memory devices.

Dislocation structure of deformed olivine single crystals from conventional EBSD maps

Dislocations, linear defects in a crystalline lattice characterized by their slip systems, can provide a record of grain internal deformation. Comprehensive examination of this record has been limited by intrinsic limitations of the observational methods. Transmission electron microscopy reveals individual dislocations, but images only a few square $$\upmu$$ μ m of sample. Oxidative decoration requires involved sample preparation and has uncertainties in detection of all dislocations and their types. The possibility of mapping dislocation density and slip systems by conventional (Hough-transform based) EBSD is investigated here with naturally and experimentally deformed San Carlos olivine single crystals. Geometry and dislocation structures of crystals deformed in orientations designed to activate particular slip systems were previously analyzed by TEM and oxidative decoration. A curvature tensor is calculated from changes in orientation of the crystal lattice, which is inverted to calculate density of geometrically necessary dislocations with the Matlab Toolbox MTEX. Densities of individual dislocation types along with misorientation axes are compared to orientation change measured on the deformed crystals. After filtering (denoising), noise floor and calculated dislocation densities are comparable to those reported from high resolution EBSD mapping. For samples deformed in [110]c and [011]c orientations EBSD mapping confirms [100](010) and [001](010), respectively, as the dominant slip systems. EBSD mapping thus enables relatively efficient observation of dislocation structures associated with intracrystalline deformation, both distributed, and localized at sub-boundaries, over substantially larger areas than has previously been possible. This will enable mapping of dislocation structures in both naturally and experimentally deformed polycrystals, with potentially new insights into deformation processes in Earth’s upper mantle.

Preparation and characterization of Black titanium by chemical reduction of TiO2 and its photocatalytic activity

Background: Monitoring of the chemical synthesis of black titanium. Objective: In this study, we prepared a black titanium nanomaterial by chemical reduction (NaBH4 treatment). Control of the black TiO2 nanomaterial synthesis followed by a thermal analysis from 100°C to 400°C under azote atmosphere is presented. We used a commercial dye, Reactive Bezactiv Yellow (RBY) degradation, to examine the photocatalytic activity of the black titanium. Method: The thermal analysis of WT and a mixture of treated TiO4 (WT+NaBH2) was examined by thermogravimetric analysis (TGA). Results: A deformation of the crystalline lattice is extended beyond the entire visible spectrum. The thermal property reveals that the black titanium is more stable than the white titanium, and BT indicated a more photocatalytic performance than WT. Conclusion: We have successfully synthesized black titanium via chemical reduction employing a synthesis of white titanium. The thermal analysis reveals that BT has a high resistance than WT that offers a promising opportunity for several photocatalytic applications.

Photodegradation of Methylene Blue and Evans Blue by Iron and Sulphur Doped TiO2 Nanophotocatalyst under Ultraviolet and Visible Light Irradiation

This research firstly aims to fabricate and characterize doped TiO2 nanoparticles (NPs) by iron and Sulphur dopants, and then the determination of the photocatalytic activity of NPs. Titanium tetraisopropoxide (TTIP), iron trichloride hexahydrate, thiouria, glacial acetic are utilized as precursors in the hydrothermal method without using a template or surfactant. The synthesized NPs are investigated by X-ray diffraction (XRD), field emission electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), N2 adsorption-desorption, UV-Vis spectroscopy, UV-Vis diffuse reflectance spectroscopy (DRS) and Fourier transform infrared (FT-IR). The lattice constants, strain, stress, deformation energy density and crystallite size are investigated using Williamson-Hall (W-H) and Wagner-Halder (W-H) models by considering the different isotropic nature of the crystalline lattice. The X-ray analysis indicates the tetragonal anatase phase without dopant crystalline phases. The FE-SEM and TEM images reveal a granular shape of NPs with a mean diameter of about 35 nm. Decoloration or photodegradation of organic dyes such as methylene blue (MB) and Evans Blue (EV) under UV-Vis irradiation is a method to measure the photocatalytic activity of doped TiO2 NPs. The results indicate the significant effect of dopants on the photocatalytic activity of doped TiO2 NPs, so that in comparison with other studies, it has a higher performance and removal efficiency. The bandgap of NPs is estimated from the Kubelka-Munk theory to be 2.87 eV. Resumen. Esta investigación tiene como objetivo fabricar y caracterizar nanopartículas de TiO2 (NP) dopadas con hierro y azufre, y la actividad fotocatalítica de las NP. El tetraisopropóxido de titanio (TTIP), el tricloruro de hierro hexahidratado, la tiouria, el acético glacial fueron los precursores en la síntesi según el método hidrotermal y no se utilizó una plantilla o tensioactivo. Las NP sintetizadas se caracterizaron por difracción de rayos X (XRD), microscopía electrónica de emisión de campo (FE-SEM), espectroscopía de rayos X de dispersión de energía (EDX), microscopía electrónica de transmisión (TEM), adsorción-desorción de N2, espectroscopías UV-Vis, de reflectancia difusa UV-Vis (DRS) e infrarroja por transformada de Fourier (FT-IR). Las constantes de red, deformación, tensión, densidad de energía de deformación y tamaño de cristal se investigan utilizando modelos de Williamson-Hall (W-H) y Wagner-Halder (W-H), considerando la diferente naturaleza isotrópica de la red cristalina. El análisis de difracción de rayos X indica la fase anatasa tetragonal sin fases cristalinas dopantes. Las imágenes FE-SEM y TEM revelan una forma granular de las NP, con un diámetro promedio de aproximadamente 35 nm. La decoloración o fotodegradación de tintes orgánicos como el azul de metileno (MB) y el azul de Evans (EV) bajo irradiación UV-Vis es un método para medir la actividad fotocatalítica de las NP de TiO2 dopadas. Los resultados indican un efecto significativo de los dopantes sobre la actividad fotocatalítica de las NP de TiO2 dopadas, que, en comparación con otros estudios, tiene un mayor rendimiento y eficiencia de eliminación. La bandgap de las NP se estimó en 2.87 eV, a partir de la teoría de Kubelka-Munk.