X-ray Powder Diffraction Methods Research Articles

High-valent oxovanadium metallosupramolecular species as catalysts for the oxidation of benzyl alcohol derivatives.

Coordination-driven synthesis has been successfully utilized to prepare vanadium-based metallosupramolecular species. By systematically varying synthesis methods and reaction conditions, two series of isostructural oxovanadium(v) coordination polymers [VO(SIH)(OR)] n (where SIH2- represents salicylaldehyde isonicotinoylhydrazonate, and R corresponds to CH3 (1β·0.25CH3OH), C2H5 (2α and 2β·0.25C2H5OH), C3H7 (3α), C4H9 (4α and 4β), and C5H11 (5β)), were synthesized. Additionally, a phase-pure tetranuclear compound [VO(SIH)(OCH3)]4·4CH3OH (1t·4CH3OH) was also prepared. In these compounds the [VO(SIH)] units, featuring the isonicotinoylhydrazonate heterocyclic moiety, are interconnected through V-Nisonicotinoyl coordination bonds. This linkage enables formation of the one-dimensional (1D) zig-zag chain compounds and zero-dimensional (0D) metallocycle, as determined by single crystal X-ray crystallography. This study further explored the formation and transformation of the assemblies, thereby emphasizing the influence of the ancillary OR- ligand. The compounds were also characterized by powder X-ray diffraction, chemical analysis, thermogravimetric (TGA) measurements, and spectroscopic methods (IR-ATR, UV-Vis, and NMR). The catalytic activity of vanadium coordination entities 1t and 1β was tested for the oxidation of benzyl alcohol and its derivatives, including 2-nitrobenzyl, 2-chlorobenzyl, and 2-methylbenzyl alcohol. Several oxidizing agents were used, including tert-butyl hydroperoxide (TBHP) in aqueous and decane solutions, as well as hydrogen peroxide (H2O2). The study also assessed the impact of different solvents, such as toluene, acetonitrile, and methanol, thereby enhancing the understanding of these systems.

Room-Temperature-Stabilized Alpha Tin Nanocrystals for In Vivo Toxicology Evaluation and Photothermal Therapy Corroborated by FFT Modeling.

Herein, we unveil a remarkable finding for synthesizing room-temperature-stable, nontoxic, ultrasmall free-standing diamond cubic tin nanocrystals (α-Sn) with beta forms in the aqueous phase, avoiding conventional approaches that typically use toxic elements or large reactive substrates (Si/InSb) to stabilize α-Sn above 13 °C. Herein, for the first time, we demonstrate the successful synthesis of free-standing alpha tin with extraordinary stability up to 80 °C and in the aqueous phase at room temperature, which was supported by powder X-ray diffraction and X-ray photoelectron spectroscopy characterization methods. This synthetic approach eliminates the need to use hazardous materials, bulky substrates, and elevated temperatures, offering a safer, low-cost, and more sustainable alternative. Prepared α-Sn is characterized by extraordinary NIR absorption and a photothermal efficiency of 42.4%, making it a promising photothermal agent for cancer treatment upon shining low-power (0.5 W) 980 nm NIR light using a CW laser. Using fast Fourier transform weighted bright-field imaging, a mathematical model that foretells the behavior of live malignant cells before and after photothermal treatment has been constructed. Additionally, in vivo studies in rats backed by biochemical and histopathological analyses demonstrated no adverse effects on the vital organs of Wister rats. The unusual biocompatibility of the prepared α-Sn nanocrystals is demonstrated by a low hemolysis index (3.28 ± 0.53%) of the blood, which is far below the permissible limits of 5%. Current research unveils the strong potential of free-standing alpha-tin not only in the area of nanomedicine but also in other domains.

Utilization of Bottom Ash from Biomass Combustion in a Thermal Power Plant to Remove Cadmium from the Aqueous Matrix.

This study provides a cost-effective method for using bottom ash from biomass combustion, which would otherwise constitute waste, to remove cadmium from acidic industrial wastewater. The X-ray powder diffraction method was used to identify the crystal forms, i.e., the arrangement of atoms in the crystal lattice, and to determine the composition of bottom ash, and the X-ray fluorescence method was used to obtain information on the elemental composition of bottom ash. The Fourier Transform Infrared method was used to analyse and identify the different functional groups occurring in bottom ash. Scanning Electron Microscopy with energy-dispersive X-ray was used to obtain detailed information on the bottom ash surface. The effect of various factors on Cd removal was studied, and optimal experimental conditions were found. The kinetic and thermodynamic equations showed that the removal of Cd2+ using bottom ash from biomass combustion was a single-layer chemical adsorption meeting the requirements of pseudo-second-order kinetics. The limiting parameter for the effective adsorption of Cd2+ using bottom ash from biomass combustion is its alkaline nature. It can only be used for solutions with pH < 2, which, on the other hand, is its advantage in practical application, namely, in the final treatment of acidic industrial wastewater.

Thin Films of BaM Hexaferrite with an Inclined Orientation of the Easy Magnetization Axis: Crystal Structure and Magnetic Properties.

Thin (~50 nm thick) BaM hexaferrite (BaFe12O19) films were grown on (1-102) and (0001) cut α-Al2O3 (sapphire) substrates via laser molecular beam epitaxy using a one- or two-stage growth protocol. The advantages of a two-stage protocol are shown. The surface morphology, structural and magnetic properties of films were studied using atomic force microscopy, reflected high-energy electron diffraction, three-dimensional X-ray diffraction reciprocal space mapping, powder X-ray diffraction, magneto-optical, and magnetometric methods. Annealed BaFe12O19/Al2O3 (1-102) structures consist of close-packed islands epitaxially bonded to the substrate. The hexagonal crystallographic axis and the easy axis (EA) of the magnetization of the films are deflected from the normal to the film by an angle of φ~60°. The films exhibit magnetic hysteresis loops for both in-plane Hin-plane and out-of-plane Hout-of-plane magnetic fields. The shape of Mout-of-plane(Hin-plane) and Min-plane(Hin-plane) hysteresis loops strongly depends on the azimuth θ of the Hin plane, confirming the tilted orientation of the EA. The Mout-of-plane(Hout-of-plane) magnetization curves are caused by the reversible rotation of magnetization and irreversible magnetization jumps associated with the appearance and motion of domain walls. In the absence of a magnetic field, the magnetization is oriented at an angle close to φ.

Lignin-Derived Carbons for Electrocatalytic Oxygen Reduction Reaction in Alkaline Media

With the Paris agreement, many countries around the world have set ambitious decarbonization goals. Due to high abundance and greenhouse gas emitting index, there is a growing interest toward conversion of lignocellulosic biomass into materials used in the production of electrodes for batteries, fuel cells and supercapacitors. Lignin-derived carbons could substitute fossil fuel-based acetylene black. However, there are many challenges facing production of electrode-grade carbon from lignin. They include, control of inorganic impurities such as SiO2, porosity and conductivity. Lignin source and extraction processes also lead to many undesired impurities and batch to batch variability.Carbon black alone is known to catalyze the oxygen reduction reaction (ORR), a key catalytic reaction controlling performance of metal-O2 batteries and fuel cells. The ORR can proceed via sequential 2-electron (2e) or a more desirable direct 4-electrons (4e) reduction pathway depending on the chemical identity of the active material.1-2) In this presentation, we will report on the physio-chemical properties of kraft lignin-derived carbons and their application in formulation of catalytic inks for electrocatalytic applications. In particular, we will discuss the effect of lignin source and pyrolysis parameters on the ORR performance in alkaline media.Lignin-derived carbons were characterized by powder X-ray diffraction, SEM-EDX, Raman spectroscopy and electrochemical methods. The catalytic activities of the electrodes prepared using lignin-derived carbons were studied by linear swept voltammetry (LSV) and rotating disk electrode (RDE) methods. Fig. 1 shows LSV of commercial acetylene black and pine-wood derived carbon, after three-steps pyrolysis. The ORR onset potential and a half-wave potential is 0.81 and 0.72 V vs. RHE, for the lignin carbon, which is closer to the half-wave potential of the widely-used 40% Pt/C catalyst. The electron transfer number, obtained from the Koutecky-Levich analysis, was 1.5, suggesting 2e reduction process.References1) Donghui Guo et al., Active Sites of Nitrogen-doped Carbon Materials for Oxygen Reduction Reaction Clarified using Model Catalysts.Science351,361-365 (2016).2) R.P. Putra, Y. Samejima, S. Nakabayashi, H. Horino, I.I. Rzeznicka, Copper-based Electrocatalyst Derived from a Copper Chelate Polymer for Oxygen Reduction Reaction in Alkaline Solutions, Catalysis Today, (2020).AcknowledgementsThis work was supported by JST Strategic International Collaborative Research Program (SICORP), Grant Number JPMJSC2302, Japan. Fig 1. LSV in the ORR region in 1 M KOH for acetylene black and lignin-derived carbon. Figure 1

Natural arsenic bronze from the Varten Kamak copper occurrence, SW Bulgaria

In contrast to the traditionally offered methods for metallurgical production of the first bronze for mankind – arsenic bronze, the present study examines another possible natural source of this alloy. Geologically, the only deposit of native copper has been localized near the Varten Kamak hamlet in the area of the town of Boboshevo, SW Bulgaria. Samples of copper nugget were investigated by the methods of powder X-ray diffraction (XRD) and scanning electron microscopy with a microprobe for elemental composition (SEM-EDS). The results show that the analyzed substance is a single-phase solid solution of Cu and As, with As content up to 3.77%, which, according to the accepted nomenclature of archaeometallurgists, is called arsenic bronze. The present study offers a new perspective on the possible sources of arsenic bronze, which may enrich the archaeological sciences.

Two new Mn-LMOF based on an AIEgens ligand for selective detection of Al3+ and other ions in aqueous solution

Two novel multifunctional chemical sensor Mn-LMOF, namely, [Mn2(TPPE)(ndc)2(H2O)]n (LMOF-1) and [Mn2(TPPE)(oba)2]n (LMOF-2) were solvothermally synthesized by introducing an AIE luminogens (AIEgens) ligand, 1,1,2,2-tetra[4-(pyridin-4-yl)phenyl]ethylene(TPPE), and analyzed by single crystal X-ray diffraction, thermogravimetric and powder X-ray diffraction and other methods. LMOF-1 and LMOF-2 have high stability and strong luminescence properties in solutions. The sensing experiments testify that LMOF-1 can be used as a selectively sensor for Al3+, with the limit of detection is 1.83 × 10−5 M. And LMOF-1 and LMOF-2 can identify Fe3+, CrO42− and Cr2O72− ions in aqueous solution, and LMOF-1 has a higher Ksv for all three ions than LMOF-2.

СИСТЕМА La–Ni–In: ФАЗОВІ РІВНОВАГИ ТА КРИСТАЛІЧНІ СТРУКТУРИ СПОЛУК

Interaction between the components in the La–Ni–In system was investigated by X-ray powder diffraction and, partially, scanning electron microscopy with energy-dispersive X-ray spectroscopy. Isothermal section of the phase diagram was constructed in full concentration range at 870 K (0–0.333 at. part La) and 670 K (&gt; 0.333 at. part La). The samples were synthesized in an arc-furnace on a water-cooled Cu-plate under an argon atmosphere and annealed in silica tubes at 870 K for one month (range 0–0.333 at. part. La) and at 670 K (range &gt; 0.333 at. part. La) for two months. The phase analysis was performed by X-ray powder diffraction method. Microstructures of polished samples and quantitative and qualitative analysis were carried out on a Tescan Vega 3 LMU scanning electron microscope equipped with an Oxford Instruments SDD X-MaxN20 detector. Fourteen ternary compounds, namely LaNi7In6 (LaNi7In6-type structure), LaNi9In2 (YNi9In2-type structure), LaNi3In6 (LaNi3In6-type structure), LaNi5In (CeNi5Sn-type structure), LaNi3In2 (HoNi2.6Ga2.4-type structure), LaNiIn4 (YNiAl4-type structure), La4Ni7In8 (Ce4Ni7In8-type structure), La5Ni6In11 (Pr5Ni6In11-type structure), LaNi2In (PrCo2Ga-type structure), LaNiIn (ZrNiAl-type structure), LaNi0.5–0.25In1.5–1.75 (AlB2-type structure), La2Ni2In (Mo2FeB2-type structure and о-La2Ni2In-type structure), La11Ni4In9 (Nd11Pd4In9-type structure), La12Ni6In (Sm12Ni6In-type structure) exist in the La–Ni–In system at the temperature of investigation. The crystal structure of о-La2Ni2In and La12Ni6In compounds was refined using powder data (STOE STADI P, Cu Kα1–radiation). The substitution of Ni for In was observed for compounds with AlB2- and YNi9In2-types structure and its composition can be described by the formulas LaNi0.5–0.25In1.5–1.75 and LaNi9–8.2In2–2.8 respectively. Binary compound LaNi5 dissolves up to 8.5 at. % of In and La2In – up to 5 at. % of Ni. Compounds of the La–Ni–In system can be divided into three groups: nickel-rich compounds are complex multi-layered with high values of coordination numbers of atoms; compounds of the middle part of the concentration triangle – two-layered compounds with coordination polyhedra in the form of prisms; compounds rich in lanthanum are complex multi-layered compounds with relatively low values of coordination numbers of atoms.

STUDY OF THE STRUCTURAL AND ELECTROMAGNETIC CHARACTERISTICS OF FERROMAGNETIC-DIAMAGNETIC COMPOSITES OBTAINED BY THE METHOD OF MODIFIED CHEMICAL CO PRECIPITATION

The microwave electromagnetic properties of ferromagnetic-paramagnetic and ferromagnetic-diamagnetic composites can be changed by varying the concentration of diamagnetic (paramagnetic) and ferromagnetic components. To implement the task of introducing such composites into production, research is required to find effective and simple synthesis technologies that make it possible to vary the content of components with different magnetic characteristics. This work demonstrates a simple method for the synthesis of ferromagnetic ((NiZn)Fe2 O4 )- diamagnetic (ZnO) composites by modified chemical deposition followed by annealing. Also, a comprehensive study of the structural and electromagnetic characteristics of experimental samples was carried out. Using the powder X-ray diffraction method, it was revealed that the phase composition of the final samples is represented exclusively by diamagnetic and ferromagnetic phases. Using scanning electron microscopy, it was found that after thermal annealing the powders have submicron sizes with an average size of 100–137 nm. Using vibration magnetometry, magnetic hysteresis loops were measured, the analysis of which showed that an increase in the concentration of the diamagnetic phase leads to an increase in the coercive force of the composites. The measured microwave spectra of complex magnetic permeability show that by changing the ratio between the ferromagnetic and paramagnetic phases, it is possible to realize a frequency shift of natural ferromagnetic resonance. Also, through the calculation of the reflection coefficient on a metal plate, it is shown that the resulting composites can be used as the basis for new radio-absorbing materials. In addition, the synthesized powders can also be used to create microwave devices and microwave antennas.

Design and fabrication of a novel platform for detection of 5-fluorouracil as the anti-cancer drug using COFs/MOFs nanocomposite with graphene quantum dots

In this study, a novel modified electrode based on the covalent organic frameworks (COFs) Schiff base network-1 (SNW-1) hybridized with copper-based metal–organic frameworks (Cu-MOFs) embedded by graphene quantum dots (GQDs) nanocomposite at the glassy carbon electrode, SNW-1/Cu-MOFs/GQDs/GCE, was reported. The purpose of this modification is to enhance the detection capabilities of the constructed modified electrode for the 5-Fluorouracil (5-FU), an anti-cancer drug, by increasing its electrocatalytic activity towards the oxidation of 5-FU molecules. The SNW-1/Cu-MOFs/GQDs nanocomposite was effectively characterized by the various physicochemical analyses techniques including field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, tunneling electron microscopy, Brunauer-Emmett-Teller (BET), X-ray powder diffraction and electrochemical methods. Electrochemical studies showed that the modified electrode, SNW-1/Cu-MOFs/GQDs/GCE, has better electrocatalytic performance for oxidizing of the 5-FU compared to the unmodified GCE, GQDs/GCE, SNW-1/GCE, Cu-MOFs/GCE and SNW-1/Cu-MOFs/GCE. This enhancement can be attributed to large surface area, good electrical conductivity, enhanced electron transport capability of the SNW-1/Cu-MOFs/GQDs and also synergistic effect of the SNW-1/Cu-MOFs with GQDs. In optimized conditions, the SNW-1/Cu-MOFs/GQDs/GCE sensor demonstrates excellent properties including a wide linear response ranges (0.01–32 and 32–65 μM), low detection limit (35 nM), high sensitivity (3.8 μAμM-1cm2), long-term signal stability, and reproducibility. It is worth noting that this sensor can accurately determine 5-FU in biological sample, showcasing its potential for practical analysis.

Anti-corrosion investigation of silver coated starch-chitosan nanocomposite on Al in NaOH wash solution

This work focuses on the effectiveness of a Starch-Chitosan nanocomposite containing embedded silver nanoparticles in preventing the Al corrosion in a 3 M NaOH system. Using Fourier Transform Infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), and X-Ray Powder Diffraction (X-RD) methods, the produced polymer nanocomposite was studied. Gravimetric, impedance, potentiodynamic polarization and SEM//EDAX techniques were used to test the efficiency of Starch-Chitosan nanocomposite embedded with silver nanoparticles (Ag@Starch-CS polymer nanocomposite) as an eco-friendly inhibitor. Activation parameters and adsorption isotherm support both physical and chemical adsorption mechanisms with robust protection efficiency. The Tafel curves validated that, Ag@Starch-CS polymer nanocomposite performs as an anodic type of corrosion inhibitor. The presence of OH, NH2, etc., groups in Ag@Starch-CS polymer nanocomposite was found to have contributed significantly to the inhibition process by interacting with the Al surface.

Heteronuclear Complexes of Hg(II) and Zn(II) with Sodium Monensinate as a Ligand.

The commercial veterinary antibiotic sodium monensinate (MonNa) binds mercury(II) or zinc(II) cations as thiocyanate [Hg(MonNa)2(SCN)2] (1) or isothiocyanate [Zn(MonNa)2(NCS)2] (2) neutral coordination compounds. The structure and physicochemical properties of 1 and 2 were evaluated by the methods of single crystal and/or powder X-ray diffraction, infrared, nuclear magnetic resonance, X-ray photoelectron spectroscopies, and electrospray-mass spectrometry. The primary cores of the two complexes comprise HgS2O2 (1) and ZnN2O2 (2) coordination motifs, respectively, due to the ambidentate binding modes of the SCN-ligands. The directly bound oxygen atoms originate from the carboxylate function of the parent antibiotic. Sodium cations remain in the hydrophilic cavity of monensin and cannot be replaced by the competing divalent metal ions. Zinc(II) binding does not influence the monensin efficacy in the case of Bacillus cereus and Staphylococcus aureus whereas the antimicrobial assay reveals the potential of complex 2 as a therapeutic candidate for the treatment of infections caused by Bacillus subtilis, Kocuria rhizophila, and Staphylococcus saprophyticus.

Structural, spectroscopic and improved photoelectrochemical properties of TiO2/C composites with anatase/brookite matrix, prepared by air-thermolysis of microspherical titanium glycolate

X-ray powder diffraction, Raman spectroscopy, HRTEM, electron diffraction and differential thermal analysis methods were used to study structural and spectroscopic properties and thermal stability of the products obtained by air-thermolysis of Ti-glycolate in the temperature range 300–450°С. TiO2/C composites were obtained, which have anatase/brookite matrix with a variable degree of crystallinity and contain different contents of brookite and free polymeric-like carbon with COO− groups. It was found that the residual content of carbonaceous component and the intensity of exothermal decomposition of Ti-glycolate have an effect on the formation of brookite-rich TiO2 matrix. Correlations between the phase composition and the free carbon content suggest that during crystallization brookite/carbon nanoparticles are more stable than anatase/carbon nanoparticles. PEC tests demonstrated that the composite photoanode, which has the greatest degree of crystallinity, the optimal carbon content and is most enriched with brookite, exhibits the greatest incident photon-to-current conversion efficiency (IPCE), and its IPCE peak value is twice as great as the IPCE peak value for Degussa P25. The increased IPCE value is associated with the preferable formation of carbon/brookite/anatase heterostructures. The carbon component has an optical gap of approx. 1.1 eV, and at the optimal contents it ensures efficient photogeneration and transfer of electrons into the conduction band of brookite and then into the conduction band of anatase. HRTEM study demonstrated the formation of such heterostructure with anatase/brookite heterojunction.

Fabrication of Zeolitic imidazolate framework-8 (ZIF-8) modified screen-printed electrode and its catalytic role for the electrochemical determination of biological molecule (dopamine)

Herein, we reported the simple room temperature synthesis of zeolitic imidazolate framework-8 (ZIF-8). The crystallinity and phase of the synthesized ZIF-8 was confirmed by employing powder X-ray Diffraction (PXRD) method. Field emission scanning electron microscopy (FE-SEM) results showed that synthesized ZIF-8 has rhombic dodecahedral structure. The energy-dispersive X-ray spectroscopic (EDX) and photoelectron X-ray spectroscopic (XPS) analysis showed the presence of good phase purity of the synthesized ZIF-8. The screen printed carbon electrode (SPE) has been modified using ZIF-8 as catalyst for the detection of dopamine (DA). The ZIF-8@SPE demonstrated good electrochemical performance for the sensing of DA using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The ZIF-8@SPE exhibits decent limit of detection (LOD), linear range, and sensitivity of 0.087 µM, 2–50 µM, and 4.78 µA/µM.cm2, respectively. The ZIF-8@SPE also demonstrated good reproducibility, repeatability of 50 cycles and storage stability of 30 days with insignificant change in the performance. The ZIF-8@SPE exhibited decent selectivity for the sensing of DA in presence of various interfering molecules/compounds.We believe that the present work would be beneficial for the scientific scholars working on the development of DA sensors for practical applications.

Esterification catalytic over Imidazolium Ionic Liquid Modified salt of phosphotungstic Acid catalyst

A solid acid was prepared by the reaction of phosphotungstic acid (HPW)with 1-methy- limidazolium sulfobutyrolactone (MIMSB) and characterized by the methods of X-ray powder diffraction, FT-IR, potentiometric titration and SEM. Then the solid acid was employed for esterification to evaluate its acid-catalytic activity. Various reaction parameters, including catalyst dosage, reaction time, n-butanel/butyric acid molar ratio and reaction temperature were systematically examined. These results indicated that the prepared catalyst maintained the Keggin structure of the raw HPW, and had high acidity. The catalyst exhibited excellent catalytic activity in esterification of n-butyric acid and n-butanol.93. 4% conversion of n-butyric acid was obtained under the optimized reaction conditions. The catalyst also had good stability.

Five Novel Polymorphs of Cardarine/GW501516 and Their Characterization by X-ray Diffraction, Computational Methods, Thermal Analysis and a Pharmaceutical Perspective.

GW501516, also known by the name of cardarine, is a synthetic peroxisome-proliferator-activated receptor delta (PPR-δ) agonist agent developed for applications in the treatment of metabolic disorders and cardiovascular diseases. A broad polymorph screening in various solvents and mixtures was completed in order to explore its capabilities to grow polymorphs. The crystal structures of four polymorphs were elucidated using single-crystal X-ray diffraction, while one structure was solved via a powder X-ray diffraction method. The solid state features (nature of intermolecular interactions) were investigated by computational methods. The polymorphs were further investigated by thermal DSC analysis and X-ray diffraction on powders. From a pharmaceutical perspective, the stability and solubility of the polymorphs were analyzed as well.

High-pressure/high-temperature synthesis of Ln 2CdB5O11(OH) (Ln = Tm, Lu)

Abstract This report presents work on the orthorhombic phases Ln 2CdB5O11(OH) (Ln = Tm, Lu). The title compounds were synthesized in a Walker-type multianvil device at 7 GPa and 650 °C, and the resulting samples were thoroughly investigated through single-crystal and powder X-ray diffraction methods. Lu2CdB5O11(OH) crystallizes in the space group Pmna (no. 53) with the unit cell parameters a = 12.772(2), b = 4.6017(7), and c = 12.481(2) Å. Similar unit cell parameters are observed for the isotypic Tm analogue compound. The crystals have a layered crystal structure built up by four-, five-, and eight-membered rings of corner-sharing [BO4] tetrahedra. The structural data are accompanied by attenuated total reflection (ATR) infrared spectra and energy-dispersive X-ray spectroscopy (EDX).

Structural anatomy and thermal transitions of barium feldspars, BaAl2Si2O8

BaAl2Si2O8 (barium feldspar-based) materials are widely used in glass and ceramic industry due to high melting temperature, chemical resistance, low thermal expansion, low dielectric constants and attractive luminescence properties. The durability of barium feldspar ceramics strongly depends on reversible phase transitions between the low-temperature modification (celsian), and series of high-temperature (HT) polymorphs known as 'hexacelsian'. Numerous works have been devoted to the study of the thermal transitions of 'hexacelsian' by X-ray powder diffraction methods and transmission electron microscopy, the use of which provides limited information about structural changes. Here, the crystal structures, thermal properties and phase transitions of HT BaAl2Si2O8 polymorphs are characterized for the first time using in-situ HT X-ray single-crystal structural study (SCXRD), and micro-Raman spectroscopy up to 1000 °C. The crystal structure of α-hexacelsian under ambient conditions is monoclinic (I2/a). The alpha-form undergoes two polymorphic transformations upon heating: into an orthorhombic (Fmmm) β-modification above 300 °C and into a hexagonal (P–62m) γ-modification above 700 °C. These transitions lead to significant changes in the unit-cell volume: an obstacle in the production of BaAl2Si2O8-based ceramics.

From Cs[C2N3] to Cs3[C6N9] – a thermal and structural investigation

Abstract Cesium dicyanamide Cs[C2N3] (≡ Cs[N(CN)2] or Cs[dca]) was obtained by a metathesis reaction in form of transparent colorless platelets. The results of single-crystal X-ray structure measurements and refinements (C2/c, Z = 8) with the monoclinic cell parameters a = 932.31(8), b = 1274.67(9), c = 824.94(7) pm, β = 110.803(3)° at −70 °C and a = 939.59(7), b = 1281.58(8), c = 827.57(6) pm, β = 110.610(3)° at 20 °C corroborate earlier results for this compound. The Raman and IR spectra of Cs[C2N3] are presented for the first time and the result compares well with those of NaCs2[C2N3]3. The heat-driven cyclotrimerization process of Cs[C2N3] was studied by thermal analyses (DSC) and temperature-dependent X-ray powder diffraction methods. At 370 °C, its trimerization product Cs3[C6N9] is formed, crystallizing in the orthorhombic space group Pbam with the cell parameters a = 3043.0(3), b = 1052.4(1) and c = 415.21(4) pm for Z = 4. The IR spectrum of this cesium tricyanomelaminate (Cs3[C6N9] or Cs3[TCM]) is presented, but a well-resolved Raman spectrum could not be acquired owing to fluorescence phenomena. An overview about the cyclotrimerization reactions of all pseudo-binary alkali-metal dicyanamides (A[C2N3]) to their corresponding tricyanomelaminates (A 3[C6N9]) with A = Li–Cs gives a basis for a discussion of the different thermal and structural characteristics.

Enhancing the efficiency of gas sensing on perovskite BaTiO3 nanoparticles using dynamic shock wave flow environment

The effect of nonlinear dynamic shock waves on perovskite BaTiO3 nanoparticles (NPs) is investigated using a table top pressure-driven shock tube (Reddy Tube) for ammonia gas sensing applications with the Mach number of 2.2. In general, shock waves are a nonlinear high-pressure phenomenon characterized by high dynamic pressure and temperature. Raman and powder X-ray diffraction (XRD) methods were utilized to evaluate the molecular and structural characteristics of the BaTiO3 (BTO) NPs under the influence of dynamic shock waves. The surface absorption was assessed using UV- diffuse reflectance spectroscopy (UV-DRS). XRD data shows that BaTiO3 NPs crystallized in tetragonal crystal structure with P4mm space group and stable throughout the shocks, without undergoing any phase change. The average particle size of the control BaTiO3 was 31 nm, while those of shocked BaTiO3 were 62 nm (100 shocks) and 55 nm (200 shocks), demonstrating the significant change in morphology and showing that particles have irregular spherical morphology and are agglomerated by shock wave loaded conditions. Moreover, BaTiO3 nanoparticles were shocked after being tested with various concentrations of different gases at a temperature of 200°C. Under shock loaded conditions, the heightened sensing response for ammonia gases was between 5 and 20 ppm; also, sensing properties such as sensitivity, response, and recovery time indicated that BaTiO3 nanoparticles are a good potential ammonia gas sensing material for real-time sensor applications with enhanced characteristics.