X-ray Diffractometry Results Research Articles

An integrated approach to characterize diabase sills in Parnaíba Basin, based on geochemical data, cuttings description, and well logs interpretation

Igneous rocks play a fundamental role in the formation and evolution of petroleum systems in several basins around the world. In the Parnaíba Basin, northestern Brazil, the diabase sills and dikes, which compound the Mosquito and Sardinha formations, contribute as a thermal source for an unconventional hydrocarbon generation, as well as providing trap and seal for the petroleum system. To understand these intrusions, we propose a methodology to identify the igneous intrusions in well-logs and interpret their compositional variations. The methodology is based on detailed descriptions of cuttings, X-ray fluorescence (XRF), X-ray diffractometry (XRD) and well logs, such as Gamma Ray (GR), Density (RHOZ) and Photoelectric Factor (PEFZ), from six exploratory wells drilled in the main gas-producing area of the Parnaíba Basin. The intrusions present in these wells were identified through the Igneability Feature and classified based on the GR curve as either “Barriguda” or “Caixote” patterns. The “Barriguda” intrusions show variations in the well logs (GR, RHOZ and PEFZ) along their vertical section, as well as variations in aluminum, calcium, potassium, zirconium, iron, titanium, magnesium, nickel and chromium values, evidencing a great textural and mineralogical variation, confirmed by the mineralogical results of XRD. Data interpretation suggests that the “Barriguda” intrusions are characterized in distinct electrofacies- and chemiofacies that represent an internal variation from top to base, related to magmatic differentiation processes.

Formation of nanosized copper silicides in a high-speed electric discharge plasma jet

Relevance. The search for suitable materials for creating a new generation of anodes in lithium-ion batteries that have not only high capacity, but also high electrical conductivity. For this purpose, the attempts have been made to use silicon Si, which has a high specific capacitance, instead of graphite C, but this material does not have high electrical conductivity. Copper silicides, in addition to high specific capacity, have high electrical conductivity values, since they do not react with lithium during operation, and therefore can be used to solve problems in the development of the above-mentioned lithium-ion anodes. Aim. To obtain dispersed materials in a high-speed jet of electric discharge plasma in the Cu-Si-C system. Objects. Dispersed materials obtained in the Cu-Si-C system. Methods. Plasma dynamic synthesis, X-ray diffractometry (X-ray phase analysis), scanning electron microscopy, transmission electron microscopy. Results. The authors have carried out the experimental studies to obtain dispersed materials of the Cu-Si-C system in a high-speed electric-discharge plasma jet and studied the microstructure and composition of the synthesized materials. It was revealed that the product consists of nanodispersed particles, which is confirmed by the results of scanning and electron microscopy. According to the results of X-ray diffractometry, crystalline phases of copper of the cubic system and copper silicides Cu3Si and Cu7Si of the hexagonal system are identified in the composition of the synthesized material.

Anodic Formation and Photoelectrochemical Characteristics of Ag(I) Oxide on Ag-Pd System Alloys

Silver(I) oxide is considered as one of the promising materials for photoelectrochemical technologies, since it is characterized by an optimal band gap, relatively low cost, and a wide range of production methods. However, its characteristics such as quantum efficiency, morphology and crystal structure parameters require optimization, which can be achieved by applying the most suitable method for obtaining the material. One of the fairly simple methods is the anodic oxidation of silver or its alloys in an alkaline medium, which makes it possible to obtain oxide phases with a controlled composition and predictable properties by varying the concentration of alloy components and electrolysis mode. The purpose of this work is to reveal the features of anodic formation and to determine the photoelectrochemical characteristics of silver (I) oxide on silver alloys with palladium in deaerated 0.1 M KOH. The regularities of the anodic formation of Ag(I) oxide on alloys of the Ag-Pd system with an atomic fraction of palladium from 0.05 to 0.20 in deaerated 0.1 M KOH were studied by non-stationary electrochemical methods of cyclic voltammetry, chronoamperometry with synchronous recording of photocurrent, and measurement of photopotential. The phase composition of the alloys (alpha phase) was determined from the results of X-ray diffractometry. Сhemical composition was determined by energy dispersive microanalysis. Photoelectrochemical parameters were calculated from the results of measuring the photocurrent and photopotential. It was established that the Ag(I) oxide anodically formed on silver-palladium alloys is characterized by n-type conductivity and the predominance of donor defects. On alloys with a relatively low concentration of palladium (5 and 10 at. %), Ag(I) oxide with a higher concentration of defects is formed, while on alloys with a relatively high concentration of palladium (15 and 20 at. %), with a lower concentration of defects than on silver.

Carbon-doped Bi2MoO6 nanosheet self-assembled microspheres for photocatalytic degradation of organic dyes

Abstract In this paper, carbon-doped Bi2MoO6 (C-Bi2MoO6) nanosheet self-assembled microspheres were prepared by using the solvothermal-calcination route to improve the photocatalytic activity of Bi2MoO6. The characterization results of x-ray diffractometry, Fourier transform infrared spectrometry, Raman scattering, scanning electron microscopy, transmission electron microscopy, BET specific surface area test, and x-ray photoelectron spectrometry indicated that C replaced the O2− anion in the Bi2MoO6 lattice, thinning the nanosheets, decreasing the size of the microspheres, and increasing the specific surface area of the Bi2MoO6. Ultraviolet–visible diffuse reflectance spectroscopy, photoluminescence, electrochemical impedance spectroscopy, transient photocurrent, and linear sweep voltammetry (LSV) spectroscopy demonstrated that the carbon doping reduced the band gap energy, raised the conduction band, and enhanced the photogenerated electron–hole pairs separation efficiency of Bi2MoO6. Benefiting from these favorable changes, the C-Bi2MoO6 microspheres prepared at a molar ratio of C to Bi of 4 (4C-Bi2MoO6) exhibited the highest photocatalytic activity, and the photocatalytic degradation rate constant of rhodamine B by 4C-Bi2MoO6 microspheres was almost 2.26 times that by pristine Bi2MoO6 under simulated solar light. 4C-Bi2MoO6 microspheres (0.2 g/L) presented excellent photocatalytic performance toward RhB (20 mg/L) at pH value 1 and could remove 98.31% of the RhB within 120 min. In addition, 4C-Bi2MoO6 microspheres also possessed a high photocatalytic activity toward methylene blue and tetracycline. 4C-Bi2MoO6 microspheres assembled from thin nanosheets can be used as effective photocatalysts to degrade toxic organic molecules from wastewater.

Implementation of a non-destructive method to assess weathering deterioration of sandstones in cultural heritage

This paper proposes a non-destructive approach based on the Equotip hardness tester to assess weathering deterioration in a protected sandstone monument located in the historic centre of Camerino (Italy). The approach is tested on one sandstone column, where various forms of weathering, such as discolouration, scaling and loss of stone volume, are observed. The mechanical characterisation with Equotip was performed on 24 measuring points, systematically distributed in the column. Innovatively, the two probes available from Proceq (Proceq© 2010) were used to assess differences among surface and in-depth hardness values of the column. In addition, an un-weathered rock core from the original extraction site was also analysed and compared with the rock matrix of the column. The obtained results show a 15% hardness reduction from depth to the surface of the column and a 25% overall hardness reduction with respect to the fresh sandstone core samples. Equotip results were coupled with grain size analyses, mercury intrusion porosimetry, scanning electron microscopy and X-ray diffractometry results, and a correlation between hardness and grain size was evaluated. By combining these approaches, it was possible to identify the processes that occurred during weathering: (a) freeze-thaw cycles that caused a decrease in micropore volume and an increase in macropores connected with low Equotip values; (b) iron oxide and sulphuric acid released from pyrite oxidation contribute to the dissolution and precipitation of calcium carbonate, which can be rearranged in the outer and surface macroporosity. The quantitative approach proposed in this study may be a valid low-cost and quick tool to assess weathering heterogeneities on building stone materials and to provide insights for effective preservation strategies of historical monuments.

Investigation of the Photocatalytic Performance, Mechanism, and Degradation Pathways of Rhodamine B with Bi2O3 Microrods under Visible-Light Irradiation.

In the present work, the photodegradation of Rhodamine B with different pH values by using Bi2O3 microrods under visible-light irradiation was studied in terms of the dye degradation efficiency, active species, degradation mechanism, and degradation pathway. X-ray diffractometry, polarized optical microscopy, scanning electron microscopy, fluorescence spectrophotometry, diffuse reflectance spectra, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, UV-visible spectrophotometry, total organic carbon, and liquid chromatography-mass spectroscopy analysis techniques were used to analyze the crystal structure, morphology, surface structures, band gap values, catalytic performance, and mechanistic pathway. The photoluminescence spectra and diffuse reflectance spectrum (the band gap values of the Bi2O3 microrods are 2.79 eV) reveals that the absorption spectrum extended to the visible region, which resulted in a high separation and low recombination rate of electron-hole pairs. The photodegradation results of Bi2O3 clearly indicated that Rhodamine B dye had removal efficiencies of about 97.2%, 90.6%, and 50.2% within 120 min at the pH values of 3.0, 5.0, and 7.0, respectively. In addition, the mineralization of RhB was evaluated by measuring the effect of Bi2O3 on chemical oxygen demand and total organic carbon at the pH value of 3.0. At the same time, quenching experiments were carried out to understand the core reaction species involved in the photodegradation of Rhodamine B solution at different pH values. The results of X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffractometer analysis of pre- and post-Bi2O3 degradation showed that BiOCl was formed on the surface of Bi2O3, and a BiOCl/Bi2O3 heterojunction was formed after acid photocatalytic degradation. Furthermore, the catalytic degradation of active substances and the possible mechanism of the photocatalytic degradation of Rhodamine B over Bi2O3 at different pH values were analyzed based on the results of X-ray diffractometry, radical capture, Fourier-transform infrared spectroscopy, total organic carbon analysis, and X-ray photoelectron spectroscopy. The degradation intermediates of Rhodamine B with the Bi2O3 photocatalyst in visible light were also identified with the assistance of liquid chromatography-mass spectroscopy.

Effect of organoclay on the physical properties of colorless and transparent copoly(amide imide) nanocomposites.

Copoly(amic acid) was prepared using the diamine monomer N,N'-[2,2'-bis(trifluoromethyl)-4,4'-biphenylene]bis(4-aminobenzamide) (TFAB) and the anhydride monomers 4,4'-(hexafluoro-isopropylidene)diphthalic anhydride (6FDA) and 4,4'-biphthalic anhydride (BPA). Thereafter, a colorless and transparent copoly(amide imide) (Co-CPAI) film was synthesized through various heat treatments. Co-CPAI hybrid films with a TFAB : 6FDA : BPA molar ratio of 1 : 0.5 : 0.5 were subsequently fabricated using organically modified hectorite (STN) with various contents ranging from 0 to 7 wt% via the solution intercalation method. Finally, the thermomechanical properties, clay dispersion, and optical transmittance of the hybrid films were investigated. The results of wide-angle X-ray diffractometry and transmission electron microscopy demonstrated good dispersion at low clay loadings; however, clay agglomeration was observed above a certain critical STN content. At the critical STN content of 3 wt%, the clay was evenly distributed in the matrix with a nanoscale thickness of approximately 10 nm. Hybrid films containing 3 wt% STN showed excellent thermomechanical properties. Beyond this critical clay content, the physical properties of the films decreased because of the agglomeration of excess clay. Regardless of the clay content, however, the optical properties of the hybrid films remained constant, and their yellow indices, which ranged from 2 to 4, indicated excellent colorless transparency.

Lignin activated carbon obtained by a environmentally friendly green production process using deep eutectic solvents

AbstractThe aim of this study was to produce activated carbon (AC) from lignin obtained with deep eutectic solvents (DESs) of choline chloride–lactic acid. For this, lignin particles were produced using the DES. The DES lignin (DES‐Lig) was modified with zinc dichloride, and the lignin activated carbon (lig‐AC) was produced by carbonization at 600 and 900 °C. In this study, the AC obtained from the commercial lignin was also used to determine the changes in the lig‐AC from the lignin obtained with the DES. The material properties were investigated using Brunauer–Emmett–Teller (BET) surface analysis, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA), and the structural properties were investigated with X‐ray diffractometry (XRD) of the lig‐ACs. The commercial and DES‐Lig exhibited different microscopic morphologies. The surface area of the samples generally ranged from 504 to 698 g/cm2, and they included both micro‐ and mesopores according to SEM characterization. The XRD analysis showed that the ACs obtained have an amorphous structure, and thermogravimetric analysis of the ACs exhibited similar thermal behavior to that in the literature. The best morphological structure was found in the ACs prepared from lignin with the DES at 900 °C according to the results of SEM, TGA, XRD and BET analysis. The proximate analysis showed that the best ACs contain 1.5% moisture, 6.5% volatile matter, 5.5% ash content and 86.5% fixed carbon. According to the elemental analysis, the amounts of essential elements, including C, H, N and O were investigated, and the best activated carbon was determined to be the DES‐Lig at 900 °C according to BET and the proximate fixed carbon results.

Optimization and antifungal efficacy against brown rot fungi of combined Salvia rosmarinus and Cedrus atlantica essential oils encapsulated in Gum Arabic

The stability, sensitivity, and volatility of essential oils are some of their most serious limitations, and nanoencapsulation has been considered one of the most effective techniques for solving these problems. This research aimed to investigate the incorporation of Salvia rosmarinus Speen and Cedrus atlantica Manetti (MEO) essential oil mixture in Gum Arabic (GA) and to evaluate nanoencapsulation’s ability to promote antifungal activity against two brown rot fungi responsible for wood decay Gloeophyllum trabeum and Poria placenta. The optimization of encapsulation efficiency was performed using response surface methodology (RSM) with two parameters: solid-to-solid (MEO/GA ratio) and solid-to-liquid (MEO/ethanol). The recovered powder characterization was followed by various techniques using a scanning electron microscope (SEM), X-ray diffractometry (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), and thermo-gravimetric analysis (TGA). The optimal nanoencapsulating conditions obtained from RSM were ratios of MEO/GA of 1:10 (w/w) and MEO/ethanol of 10% (v/v), which provided the greatest encapsulation efficiency (87%). The results of SEM, XRD, DLS, FTIR, and TGA showed that the encapsulation of MEO using GA modified particle form and molecular structure and increased thermal stability. An antifungal activity assay indicated that an effective concentration of MEO had an inhibitory effect on brown rot fungi. It had 50% of the maximal effect (EC50) value of 5.15 ± 0.88 µg/mL and 12.63 ± 0.65 µg/mL for G. trabeum and P. placenta, respectively. Therefore, this product has a great potential as a natural wood preservative for sustainable construction and green building.

Flavonoid-incorporated starch and poly(vinyl alcohol) film: Sensitive and selective colorimetric sensor for copper identification and quantification in beverages and environmental samples

Colorimetric sensors based on an eco-friendly sensor molecule immobilized into a polymer matrix have broad applications for detecting trace elements. However, their potential for quantitative analysis of these elements remains little explored. Here, we incorporated rutin or quercetin into films based on starch, poly(vinyl alcohol), and glycerol to detect and quantify Cu2+ in different matrices. The films were characterized by colorimetric assays, thickness, and solubility analyses, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and mechanical assays. Incorporating the flavonoids in the film decreased its solubility, tensile strength, and modulus of elasticity, while increased its cross-sectional surface irregularity. XRD and DSC results indicated an increase in film crystallinity in the presence of rutin or quercetin. FTIR analyses showed a more effective incorporation of quercetin than rutin in the polymeric matrix, which was confirmed by flavonoid release studies from the film. The film containing quercetin exhibited selectivity in identifying copper in liquid matrices, changing its color from light yellow to dark yellow. An analytical method to quantify Cu2+ was developed, presenting a linear response range of 0.20–1.20 mg L−1, with detection and quantification limits of 0.060 and 0.20 mg L−1, respectively, very lower than other methods based on polymeric matrices containing natural dyes. The method was successfully applied for Cu2+ determination in cachaça and tap water samples, achieving high accuracy (96–104% of recovery) and precision (relative standard deviation < 6.7%). Our findings represent an advancement in the field of sensors based on natural dyes, demonstrating that such sensors can achieve high sensitivity without the need for complex sample preparation methods.

Experimental investigation of a fissured rock with thermal storage potential subjected to descending amplitude low cycle impacts

As the advancement of deep earth energy engineering in the 21st century, the challenges imposed by dynamic loads and high temperatures will be increasingly regular. This paper studied the dynamic mechanical behaviors and fracture characteristics of defective red sandstone (single fissure inclination of 0°, 30°, 60°, and 90°) subjected to thermal treatments (25 °C, 200 °C, 400 °C, 600 °C, and 800 °C) under descending amplitude low cycle (DALC) impact loading. The experiments were conducted using a modified split Hopkinson pressure bar (SHPB) system, and the fracture surfaces of the failed specimens were characterized through the use of high-resolution 3D laser scanning to obtain point cloud data. Subsequently, the fractal, roughness, texture, and elevation features of fracture surfaces were analyzed using the boxing-counting method, grayscale co-occurrence matrix (GLCM), and elevation-based statistics. The scanning electron microscopy (SEM) was utilized to study the fracture micromorphology as well. Additionally, the mechanisms of damage and fracture evolution were discussed based on the results of X-ray diffractometry (XRD), synchronous thermal analysis (STA), discrete element method (DEM), and strain energy density theory. The results demonstrate that the peak stress and dynamic elastic modulus deteriorate with rising temperatures and increase with larger fissure angles. While the peak strain, strain rate, and peak stress increase factor (PIF) exhibit the opposite trend. The threshold values for the intensification of these events are 400 °C and 60°. The damage is dominated by tensile cracks, which transition to shear at 30° and 60° due to temperature dependence. Meanwhile, the fractal dimension (DC), joint roughness coefficient (JRC), second-order statistics of GLCM, and elevation eigenvalues have been modeled using multiple regression analysis to investigate their interaction with temperature and fissure angle. The best-fit models illustrate significant linear or non-linear correlations between the aforementioned parameters and the mechanical parameters. Furthermore, the magnitude and distribution pattern of thermal cracks, as well as the growth of shear fractures, are governed by the dehydration, thermal expansion, phase transition, plasticization, thermal fracture, and thermal decomposition. Finally, strain energy density theory manifests promising prospects for understanding and predicting DALC impact fracture patterns of specimens.

Improving the Thermal and Photothermal Performances of MXene-Doped Microencapsulated Molten Salts for Medium-Temperature Solar Thermal Energy Storage

Molten salts are widely used as thermal energy storage materials for solar thermal applications, but they suffer from low photothermal conversion efficiency and potential leakage and corrosion issues. In this paper, MXene doping was proposed to improve the thermal properties and photothermal conversion efficiency of microencapsulated molten salts. MXene nanomaterials, which have excellent thermal conductivity and photothermal conversion efficiency, were used to dope the molten salts. The results tested by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) indicate that MXene was well doped in the molten salt microcapsules. Fourier transformation infrared (FT-IR) spectroscopy was used to confirm that the microencapsulation of the molten salt by silica is a physical action. The results of X-ray diffractometry (XRD) show that the crystal structure of the molten salt maintained stability. The results obtained from the Hot Disk thermal constant analyzer and photothermal conversion experiments showed that thermal conductivity and photothermal conversion efficiency of the MXene-doped microcapsules were increased by 156.2% and 169.4%, respectively. The differential scanning calorimeter (DSC) results indicated that the MXene-doped microcapsules had a reduction of 49.6% in the supercooling degree. The thermal reliability of the MXene-doped microcapsules was 94.0% after 50 thermal cycles. This approach provides a promising solution for improving the thermal properties and photothermal conversion efficiency of microencapsulated molten salts for medium-temperature solar thermal energy storage.

Mineralogy and geochemical characterization of geophagic clays consumed in parts of southern Nigeria

This study seeks to determine health risk associated with consumption of clay in different areas in southern Nigeria. Different clay samples sold for consumption were purchased from Mowe, Ikorodu and Onitsha Markets in southern Nigeria. The clays were subjected to mineralogical and geochemical characterization using X-Ray Diffractometry (XRD), Fourier Transform Infrared (FTIR) and Inductively Coupled Plasma-Atomic EmissionSpectrometry. Potential health risk assessment was calculated using a standardized Hazard Quotient (HQ) and Total Hazard Index (THI). XRD and FTIR results revealed the clay contains varying percentage of quartz, kaolinite, anatase, halite, pyrite, goethite, smectite and palygorskite while geochemical analysis result revealed wide range of elemental concentration (ppm). Mean concentration (ppm) of Cu, Pb, Zn, Cr, Ni and Co from the markets are 5.8 – 8; 17.4 – 29.6; 32.4 – 95.8;111.6 – 103.4; 18.6 – 39.4 and 4 – 16.6 respectively while As was below detection limit in most of the samples. HQ values were used to calculate the THI. THI values for children and adults for Mowe market samples range from 0.9 to 2.1 and 0.5–1.1 respectively, for Ikorodu market samples, THI for children and adult ranges from 1.0- 1.8 and 0.6–1.0 respectively, while THI for children and adults for Onitsha market samples ranges from 1.5 to 2.6 and 0.8–1.84 respectively. In conclusion, children that consume clay from the markets are more exposed to non-carcinogenic risks than adults. It is therefore advisable that the clays should not be consumed for a long period of time to avoid health problems.

Controlled release of a non-steroidal anti-inflammatory drug from a photocurable polymeric calcium phosphate cement

In this research, a photocurable composite based on tetracalcuim phosphate ceramic and, hydroxyethyl methacrylate-modified poly(acrylic-maleic acid) was developed and studied as a potential drug delivery system for bone defects. Different concentrations (5, 10 and 20 wt. %) of a non-steroidal anti-inflammatory drug, Indomethacin, were loaded on to the composite and its release behavior was investigated in phosphate buffered solution during 504 h. The obtained release data were fitted by both power law (Peppas) and Weibull equations. The composites were also characterized after different soaking periods using X-ray diffractometry (XRD), scanning electron microscopy (SEM) and Fourier transforming infrared spectroscopy. The results of XRD and SEM analyses revealed the formation of nanosized needle/flake-like apatite crystals on the composites surfaces; however, better apatite formation was observed for the composites loaded with higher amounts of Indomethacin. The morphological observations and quantitative estimations revealed that the loaded composites were gradually degraded in the phosphate-buffered saline. Moreover, a controlled release of Indomethacin was found from the composites in which a higher drug concentration led to a more drug level as well as sustained release profile. In drug release modeling, better regression coefficient was obtained from the Weibull equation, compared to the power law, meaning that the Weibull equation suggests a better description of the indomethacin release from the composites during the whole period of the test. In conclusion, the photocurable composite with apatite formation ability can be successfully used for the controlled release of indomethacin as an anti-inflammatory drug in bone defects.

Decisive role of microstrains in the formation of the domain structure in multiwall carbon nanotubes

The present paper deals with the structure of carbon nanotubes of various diameters. The results of X-ray diffractometry and transmission electron microscopy are analyzed in detail. It is shown that the studied carbon nanotubes have one or several types of domain boundaries (zigzag, armchair). The role of uniaxial microstrains in the formation of the domain structure in carbon nanotubes is great. The number of significant independent microstrains determines the number of the domain types in the MWCNT structure. Tubes experiencing only the εzz strain have a single-domain structure. Multiwall carbon nano-tubes with strains εzz and εxx have a multidomain structure. Nonequilibrium microstrains at interfaces during energy dissi-pation can lead to the hysteresis of thermal and mechanical properties.

Electromagnetic properties of composite filaments with ferromagnetic fillers for 3D printing

The paper presents the results of a study of composite materials based on the polymer acrylonitrile styrene acrylate (ACA) and filler M-type hexaferrite (BaFe12O19). The results of X-ray diffractometry of hexaferrite powder are presented. The porosity of the obtained composite filament samples was studied. After 9 extrusion cycles, the porosity is reduced to less than 1%. In the EHF range, the transmission coefficient through a sample of a composite material was measured. A sharp decrease in the transmission coefficient is observed in the frequency range from 42 to 55 GHz, which is due to the natural ferromagnetic resonance in BaFe12O19 hexaferrite.

ОПРЕДЕЛЕНИЕ ПАРАМЕТРОВ УРАВНЕНИЯ СОСТОЯНИЯ МОЛЕКУЛЯРНЫХ КРИСТАЛЛОВ НА ОСНОВЕ ДИФРАКТОМЕТРИЧЕСКИХ ИССЛЕДОВАНИЙ

The paper presents the results of determining the crystal structure of PETN, hexogen, and HMX samples by X-ray diffractometry and calculations of the unit cell parameters of molecular crystals associated with the processing of X-ray diffractometry results, and experimental relationships between the unit cell volumes of molecular crystals on temperature. The obtained experimental data on the isobaric compression and expansion of the studied molecular crystals allowed us to specify the thermal component of the equations of the state of molecular crystals and obtain an expression for the isobaric thermal expansion coefficient associated with the mathematical model of the thermal component of the equations of state of molecular crystals. The obtained analytical dependence of the isobaric coefficient of thermal expansion on the temperature of the considered samples correctly describes the limiting transition to low temperatures. We propose a method of approximation for the obtained experimental relationships between temperature and the unit cell volume of the studied substances under isobaric compression/expansion based on a mathematical model of the semi-empirical equations of state of molecular crystals. This approach allowed us to obtain analytical relationships between the crystal unit cell volume and temperature, which describes the results of X-ray diffractometry of the molecular crystal samples considered in the work with an accuracy of up to 3 %.

Characterization of Avocado (Persea americana) Seed Starch - Physicochemical and Powder Properties

Introduction: Starch is a biopolymer commonly used as an excipient in pharmaceutical formulations due to its biocompatibility, inertness, biodegradability, availability and affordability. Purpose: The study aimed to extract and characterize the starch isolated from avocado (Persea americana) seeds and investigate its disintegrant and binder properties in paracetamol tablet formulations. Methods: Starch was extracted from avocado seed using standard methods and then subjected to some phytochemical, physicochemical and bulk powder properties analyses. High-resolution analyses using differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and x-ray diffractometry (XRD) were also carried out on the extracted starch powder. Results: Starch extraction yield was 19.61% and the starch was light-brown in colour, odourless, tasteless and smooth in texture. The starch showed a melting point range of 102-114°C and moisture content of 22.7%. It also exhibited a hydration capacity of 2.76 g/g and swelling and moisture sorption capacities of 46.43 and 115.34%, respectively. The starch powder was cohesive with poor flow properties but the DSC, FTIR, SEM and XRD results showed a semi-crystalline powder composed of fluffy discrete particles. Conclusion: The starch isolated from P. americana seeds exhibited good swelling, hydration and moisture sorption capacities, making it a good candidate as a tablet disintegrant. Keywords: Avocado, starch, physicochemical, high-resolution, analyses

Structural evolution of Na-rich spinel oxides involving anionic redox reaction for Na-ion batteries

Two sodium-rich transition metal (TM) oxides with the same spinel structure, Na2MoO4 and Na2WO4 have been investigated as cathode materials for Na-ion batteries for the first time. Although the oxidation state of TMs in the compounds are already at its highest value of 6+, both of them can be activated by anionic redox reaction during initial charge, as revealed by X-ray photoelectron spectroscopy, to give considerable reversible capacity between 1.2 and 4.7 V. In addition, ex-situ X-ray diffractometry (XRD) shows that both cathode materials undergo insignificant structural evolution during Na extraction/insertion, suggesting that the Mo-O4 and W-O4 tetrahedral framework are stable even when more than 1 Na is removed from the materials. Overall, Na2WO4 shows larger amount of Na extraction/insertion and better cycle stability than Na2MoO4. This is likely due to better structural integrity and better stability of Na2WO4 against oxygen loss from ex-situ XRD and differential electrochemical mass spectrometry results.

Effect of Nanodiamond Content in the Plating Solution on the Corrosion Resistance of Nickel–Nanodiamond Composite Coatings Prepared on Annealed 45 Carbon Steel

A nickel-nanodiamond composite coating was prepared on the surface of annealed 45 carbon steel by double-pulse electrodeposition. The effect of nanodiamond particle content on the surface morphology, grain size and wear and corrosion resistance of the composite coating were investigated. According to the analysis of the test results of X-ray diffractometry and scanning electron microscopy, it was found that the cathodic polarization of the electrodeposition process was enhanced after the addition of nanodiamond particles to the Watts nickel plating solution. The positively charged nanodiamond particles on the surface facilitate the reduction reaction at the cathode. Nanodiamond particles provide crystalline growth sites for the non-spontaneous nucleation of nickel atoms. As the addition of nanodiamond particles increases, the diffusely distributed nanodiamond particles are able to attract more nickel ions to deposit nuclei, and its fine crystallization effect increases, resulting in improved wear resistance and corrosion resistance of the composite plating. Among the results, the polarization potential was the smallest when the nanodiamond content in the plating solution was 10 g/L. The surface of the prepared nickel-nanodiamond composite coating was relatively flat and smooth, with good density and a uniform grain size distribution, and the content of element C on the surface of the composite coating was the largest, reaching 1.99%.