Effect of Graphene Nanoparticles Addition on Superconductivity of YBa2Cu3O7~δ Synthesized via the Thermal Treatment Method

The development of high-temperature superconductor (HTS) YBa2Cu3O7~δ (Y123) bulks in industrial applications were established years ago. It is one of the developments that currently attracts great attention especially in transportation, superconductor cables and wires. This study is focused on the preparation of the Y123 bulk superconductors by the thermal treatment method due to the promising ways to develop high-quality Y123 superconductors with its simplicity, low cost, and relatively low reaction temperature used during the process. Y123 were added with graphene nanoparticles (x = (0.0–1.0) wt.%). Samples were then characterized by X-ray diffraction (XRD) analysis, field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), and alternating current susceptibility (ACS). It was found that Y123 confirmed that the majority of phases in all the XRD patterns was the orthorhombic crystal structure and the Pmmm space group with secondary phases belonged to Y2Ba1Cu1O5 (Y211). The highest Tc obtained when graphene nanoparticles were added in the Y123 sample was x = 1.0 wt.%, followed by x = 0.5 wt.% with 92.64 and 92.59 K, respectively. From the microstructure analysis, the average grain size significantly decreased to 4.754 µm at x = 0.5 wt.%. The addition of graphene nanoparticles had disturbed the grain growth of Y123, affecting the superconducting properties of the samples. On the other hand, the intergranular critical current density, Jcm, was found to increase with graphene nanoparticle addition and had the highest value at x = 1.0 wt.%, indicating that graphene nanoparticles acted as pinning centers in the Y123 matrix.

(R)-Baclofen [(R)-4-amino-3-(4-chlorophenyl)butanoic acid]

This article provides the first single-crystal XRD-based structure of enantiopure (R)-baclofen (form C), C10H12ClNO2, without any co-crystallized substances. In the enantiopure title compound, the molecules arrange themselves in an orthorhombic crystal structure (space group P212121). In the crystal, strong hydrogen bonds and C—H ... Cl bonds interconnect the zwitterionic molecules.

FORMATION OF A NOVEL DIAMOND-LIKg BILAYER BASED ON 5-7 GRAPHENE

Выполнены первопринципные расчеты структуры и свойств орторомбического графена L и нового алмазоподобного бислоя, формируемого на его основе. Расчеты методом теории функционала плотности показали, что графен L, состоящий из топологических дефектов Стоуна-Уэльса, должен устойчиво существовать при нормальных условиях, и его структура должна волнообразно гофрироваться. При сильном одноосном сжатии бислойного графена L может происходить формирование нового алмазоподобного бислоя DL. Давление фазового перехода «L → DL» составляет 10,1 ГПа, когда межслоевое расстояние в бислойном графене уменьшается до 1,61 Å. Этот бислой имеет орторомбическую кристаллическую решетку (pbam) с параметрами a = 10,145 Å и b = 5,270 А. Элементарная ячейка бислоя DL pbam содержит 32 атома углерода. Длины связей изменяются в интервале от 1,5590 до 1,6226 Å, тогда как углы между связями принимают значения от 89,62 до 140,8°. Структура алмазоподобного бислоя должна быть стабильна до 270 К. Рассчитанные значения поверхностной плотности и разностной полной энергии этого бислоя относительно полной энергии алмаза равны 1,19·10 г/см и 1,31 эВ/атом, соответственно. Бислой DL pbam должен быть полупроводником с шириной прямой запрещенной зоны 1,63 эВ. Irst-principle calculations of the structure and properties of orthorhombic L graphene and a novel diamond-like bilayer formed on its basis are performed. The calculations using the density functional theory method showed that L- graphene of Stone-Wales defects should exist stably under normal conditions, and its structure should be corrugated in a wave-like manner. Under strong uniaxial compression of bilayer L graphene, the formation of the novel diamond-like DL bilayer can occur. The pressure of the « L → DL» phase transition is 10,1 GPa, when the interlayer distance in bilayer graphene decreases to 1,61 Å. This bilayer has an orthorhombic crystal lattice (pbam) with the parameters a = 10,145 Å and b = 5,270 Å. The unit cell of the DL- pbam bilayer contains 32 carbon atoms. The bond lengths vary in the range from 1,5590 to 1,6226 Å, while the angles between these bonds range from 89,62 to 140,8°. The structure of the diamond-like bilayer should be stable up to 270 K. The calculated values of the surface density and the difference total energy of this bilayer relative to the diamond total energy are 1,19 -10 g/cm and 1,31 eV/atom, respectively. The DL pbam bilayer should be a semiconductor with a straight bandgap of 1,63 eV.

Hydrothermal synthesis of ABi2Ta2O9Aurivillius phase: A comparative study of A-site cation size on structure, dielectric, optical properties

In this study, the double-layered Aurivillius phases CaBi2Ta2O9 (CBT) and PbBi2Ta2O9 (PBT) were prepared through a hydrothermal route with NaOH as a mineralizer. XRD analysis confirmed that the CBT and PBT compounds were successfully formed and adopted an orthorhombic crystal structure with an [Formula: see text]21am symmetry. Le Bail refinements of XRD data indicated that the unit cell volume of CBT was smaller than PBT and is associated with the smaller ionic radius of Ca[Formula: see text] compared to Pb[Formula: see text]. The surface morphology of both samples, as determined using SEM, demonstrated plate-like grains with anisotropic grain growth. It was found that the different ionic radii of [Formula: see text]-site cations (Ca[Formula: see text] and Pb[Formula: see text] strongly affected the structural, optical and electrical properties of the Aurivillius phase. The occupation of smaller Ca[Formula: see text] cations induced a higher structural distortion, which resulted in higher bandgap ([Formula: see text] energy and ferroelectric transition temperature ([Formula: see text] of CBT, compared to those of PBT.

The facile one-step hydrothermal method to prepare MnO2 nanoparticles: Structural and electrochemical properties

MnO2 nanoparticles were successfully prepared via one-step hydrothermal method. The surface are properties of the MnO2 nanoparticles were determined by BET nitrogen adsorption-desorption measurement. The XRD analyses confirm the pure phase of γ-MnO2 and α-MnO2, having orthorhombic crystal structure (JCPDS file no.14-0644 and 44-0141). FE-SEM analysis reveals the combination of massively small spherical particles with average particle size 54.8 nm. The electrochemical results revealed that the MnO2 nanoparticles delivered the specific capacitance of 200.83 F/g at a current density of 1A/g. The cycle stability was usability 30% after 500 cycles at a current density of 5 A/g. The MnO2 nanoparticles reveal a energy density of 3.62 Wh/kg under a power density of 43.11 W/kg.

Barium titanate piezoelectric-film-based beam-array airflow sensor for wearable breath-monitoring application

This study presents a barium titanate (BaTiO3) film-based piezoelectric airflow sensor. This sensor integrated a piezoelectric beam array with a poly(dimethylsiloxane) orifice membrane as the core sensing component. The compact size of the micromachined device fit the requirements for a wearable device. The hydrothermally grown barium titanate film exhibited an orthorhombic crystal structure with good piezoelectric properties. We propose an algorithm to determine the airflow sensor performance using data from the measured piezoelectric signal and the displacement of the piezoelectric beam. This algorithm correlates the discharge coefficient of the core sensing component, Reynold’s number, airflow velocity, pressure difference across the component, displacement of the piezoelectric beam, strain of the barium titanate film, and generated charge from the sensor, which is rarely reported in the literature. The Young’s modulus and piezoelectric constant of the barium titanate film could also be derived as 100 GPa and 8 pC/N, respectively. Utilizing this algorithm and the generated piezoelectric signal of the sensor, important breath parameters of a young male subject at rest were monitored.

Synthesis, X-ray Structure, Conformational Analysis, and DFT Studies of a Giant s-Triazine bis-Schiff Base

The current work involves the synthesis of 2,2′-(6-(piperidin-1-yl)-1,3,5-triazine-2,4-diyl)bis(hydrazin-2-yl-1-ylidene))bis(methanylylidene))diphenol 4, characterization, and the DFT studies of the reported compound. The crystal unit cell parameters of 4 are a = 8.1139(2) Å, b = 11.2637(2) Å, c = 45.7836(8) Å. The unit cell volume is 4184.28(15) Å3 and Z = 4. It crystallized in the orthorhombic crystal system and Pbca space group. The O…H, N…H, C…H, H…H and C…C intermolecular contacts which affect the crystal stability were quantitatively analyzed using Hirshfeld calculations. Their percentages were calculated to be 9.8, 15.8, 23.7, 46.4, and 1.6% from the whole contacts occurred in the crystal, respectively. Conformational analysis was performed using DFT calculations for 17 suggested conformers and the most stable conformer was found to be the one which is stabilized by two intramolecular O-H…N hydrogen bonding interactions. This conclusion was further revealed by natural bond orbital calculations.

Growth and some surface characterization of tin Sulphide (SnS) thin film by two-electrode cell arrangement for photo absorption

This study presented deposition of tin sulphide (SnS) thin film using a two-electrode electrochemical cell arrangement. The bath electrolyte comprised tin sulphate (SnSO4 ), hydrated sodium thiosulphate (Na2S2O3∙5H2O) and sulphuric acid (H2SO4 ). The acid was used to adjust the pH of the bath. The deposited film was characterised using Surface Profilometer, X-Ray Diffractometer (XRD), Uv-Visible Spectrophotometer and four point probe technique. Surface profiling revealed that the film is continuous with thickness of about 60 nm. The XRD result showed that the film has orthorhombic crystal structure. Film's crystallite size was estimated as 0.61 nm and interplanar spacing as 0.29 nm. The Uv-visible Spectrophotometer result reveals that, the film has good absorbance but poor reflectance and transmittance in the visible light region. The film has direct allowed transition with energy band gap of 1.69 eV. Values of surface resistivity and conductivity were deduced from data obtained from Four-point probe studies as 5.12 x 10-4Ω-cm and 1.96 x 103Ω-1cm-1 respectively. The I-V characteristics curve of ITO/SnS/Ag structure is linear indicating an Ohmic contact between the substrate electrode and the deposited layer. It can therefore be suggested that the film can allow pathway for photoabsorption and also aid charge transfer in photovoltaic process. Keywords: tin sulphide, orthorhombic, electrochemical deposition, characterization, photovoltaic and surface resistivity.

Sintering behavior and microwave dielectric properties of CaTi1-x(Nb1/2Al1/2)xO3

CaTi1-x(Nb1/2Al1/2)xO3 with x=0.1-0.5 ceramics were processed through solid state sintering. X-rays diffraction (XRD) patterns of the compositions showed that the samples have orthorhombic crystal structure with symmetry (Pbnm). The symmetry was further confirmed using Raman spectroscopy. A total of 13 Raman modes were detected, which were in agreement with the XRD results. Microstructure analysis of the samples showed porosity in the samples, presumably due to the substitution of Al, having high melting point. As the concentration of Al and Nb increased, relative permittivity (er), quality factor (Q×fo) and temperature coefficient of resonance frequency decreased. Optimum microwave dielectric properties were achieved for the composition x=0.5 sintered at 1650 °C for 8 h i.e., er ~27.09, Q×fo ~17378 GHz and tf ~ -2.5 ppm/°C.

AA h BN crystal, basic structure of boron nitride nanotubes

AA h boron nitride (BN) crystal, assigned to an orthorhombic space group (No. 31, Pm21), is reported here. This new AA h BN crystal exhibits a `linear' morphology for high-resolution transmission electron microscopy (HRTEM) and a (non-hexagonal) `diagonal' electron-diffraction pattern, which have been experimentally demonstrated in this article. It is also demonstrated that this new crystal is the basic structure of multi-walled BN nanotubes (BNNTs) existing in the form of a helix. The helical AA h BNNTs exist in a metastable phase owing to 〈200〉 texture growth of the orthorhombic crystal, where the energy is ∼15 meV higher than that of stable AB or AA′ BN. It is shown that the typical scanning electron microscope `fluffy cotton-like' morphology of BNNTs is due to secondary growth of diverse BN sheets (including mono-layers) on incoherently scrolled wall strands of BNNTs, providing further evidence for the helical structure with HRTEM evidence for a left-handed helix.