Determination Of Phase Composition Research Articles

Polar-antipolar transition and weak ferromagnetism in Mn-doped Bi0.86La0.14FeO3

Having been considered as a prime example of a room-temperature magnetoelectric multiferroic, BiFeO3 continues to attract much interest. Since functional properties of this material can be effectively influenced by chemical, electrical, magnetic, mechanical and thermal stimuli, it can serve as a model for the investigation of cross-coupling phenomena in solids. Special attention is currently paid to the study of chemical pressure-driven magneto-structural transformations. In this paper, we report on the effect of the Mn doping on the crystal structure and magnetic behavior of the Bi1−xLaxFeO3 multiferroics near their polar-antipolar (antiferromagnetic-weak ferromagnetic) phase boundary. Synchrotron x-ray and neutron powder diffraction measurements of the Bi0.86La0.14Fe1−xMnxO3 (x = 0.05, 0.1, 0.15) compounds have been performed. The diffraction data suggest that the Mn substitution results in the suppression of the ferroelectric polarization and gives rise to the appearance of the antiferroelectric (generally, PbZrO3-related) phase characteristic of the phase diagrams of the Bi1−xRExFeO3 (RE = rare-earth) systems. Depending on the Mn concentration (determining phase composition of the Bi0.86La0.14Fe1−xMnxO3 samples at room temperature), either complete or partial revival of the polar phase can be observed with increasing temperature. Magnetic measurements of the samples indicate that the Mn doping affects the stability of the cycloidal antiferromagnetic order specific to the polar phase, thus resulting in the formation of a ferroelectric and weak ferromagnetic state.

Electrochemical Synthesis of Well-Ordered Macroporous Structures of Nickel – Ruthenium Alloys with Low Overpotential on Hydrogen Evolution Reaction

This work presents the results concerning electrochemical deposition of Ni-Ru alloys from aqueous acidic solutions. The Ni-Ru coatings were obtained by the potentiostatic electrodeposition on copper porous substrates and polystyrene matrix. The influence of applied potential and concentration of electroactive species on the composition and the quality of obtained coatings was determined. The elemental composition was determined with the XRF method. X-Ray analysis has been use to determine phase composition of obtained alloys. The surface morphology was investigated with the use of scanning electron microscopy. Electrochemical measurement as a linear and cyclic voltammetry was used to perform comparative examination of catalytic properties of the obtained 3-D structures in aqueous NaOH solutions. Acknowledgment The authors would like to thank Polish National Science Centre for the financial support provided by the grants: No UMO-2016/21/N/ST8/00222.

Characterization of Copper Coatings Deposited by High-Velocity Oxy-Fuel Spray for Thermal and Electrical Conductivity Applications

Copper coatings were deposited on steel substrates by high-velocity oxy-fuel spraying. The microstructure of the feedstock copper powders and free-standing coatings were evaluated by optical and scanning electron microscopy. The x-ray diffraction pattern was utilized to determine phase compositions of powders and coatings. Oxygen content was determined by a LECO-T300 oxygen determiner. The thermal conductivity of the coatings was measured in two directions, through-thickness and in-plane by laser flash apparatus. The electrical resistivity of the coatings was measured by the four-point probe method. Oxygen content of the coatings was two times higher than that of the initial powders (0.35–0.37%). The thermal and electrical conductivities of the coatings were different depending on the direction of the measurement. The thermal and electrical conductivity of the coatings improved after annealing for 6 h at a temperature of 600°C.

Aluminum hydroxide gel characterization within a calcium aluminate cement paste by combined Pair Distribution Function and Rietveld analyses

There are many commercially important multiphase materials which contain amorphous phases, such as cement pastes, porcelains, glass-ceramics or pharmaceutical compounds. However, the analysis of amorphous phase(s) within cement matrices that contain high amounts of crystalline phase(s) is a challenge. Here, we report measurements of total scattering data quantitatively analyzed by Pair Distribution Function (PDF) minimization and Rietveld methodology to determine phase compositions including both amorphous and nanocrystalline phase contents in cement-related samples. Furthermore, laboratory techniques were used to complement the sample characterization. In addition to five reference materials, the main phase of calcium aluminate cements, CaAl2O4 hydrated at 50°C to yield crystalline hydrogarnet, Ca3Al2(OH)12, (43wt%) and nanocrystalline aluminum hydroxide gel, Al(OH)3·0.1H2O (50wt%) was also investigated. The PDF analyses revealed that the hydroxide gel has a gibbsite local structure with an average particle size close to 5nm. PDF and Rietveld quantitative phase analysis results fully agree.

The effect of thermal annealing on Fe/TiO2 coatings deposited with the help of RF PECVD method. Part I. Chemical and phase composition

Results of the studies on chemical structure and phase composition of both non-annealed and thermally annealed iron doped TiO2 coatings are presented. The coatings were synthesized with the help of radio frequency plasma enhanced chemical vapor deposition (RF PECVD) and characterized by iron content in the range of 0–4.76at%. In these studies, an analysis of both elemental composition and chemical bonding was performed with the help of X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD) was applied to determine phase composition and Fourier transform infrared spectroscopy (FTIR) was used as a supplementary source of information. The obtained elemental composition data show that, apart from titanium, oxygen and iron, traces of chlorine as well as substantial amounts of carbon are present in the coatings. While chlorine has originated from plasma decomposition of TiCl4, used as a source of titanium, a presence of carbon is associated with a surface contamination resulting from photocatalytic reactions of TiO2 with the adsorbed carbon dioxide. The results of XPS and FTIR indicate that thermal annealing not only modifies phase composition of these materials, but also affects chemical bonding. Finally, XRD analysis shows that iron content has an effect on the size of coherent diffraction domains present in the films.

Technology Development of Continuous Synthesis of Active Substance for Dispenser Cathode

Barium aluminates have been obtained by the method of continuous precipitation at different values of pH. The method of thermal analysis showed that the main mass losses which are connected with dehydration processes occur in the temperature interval from 50 °C to 100 °C and from 150 °C to 200 °C. In addition, mass loss occurs in the temperature interval from 780 °C to 1000 °C which can indicate barium aluminate formation. XRD analysis was applied to determine phase composition of obtained substance and showed formation of Ba1.17Al10.67O17.17 and BaAl2O4 at pH 6.5; 7.0 and 7.5 respectively. Significant influence of pH on precipitation composition has not been detected.

Sn and Cu oxide nanoparticles deposited on TiO2 nanoflower 3D substrates by Inert Gas Condensation technique

Sn and Cu oxide nanoparticles were deposited by Inert Gas Condensation (IGC) technique combined with dc magnetron sputtering onto nanoflower TiO2 3D substrates obtained in the oxidation process of Ti-foil in 30% H2O2. Sputtering parameters such as insertion length and Ar/He flow rates were optimized taking into account the nanostructure morphology. Comparative studies with hydrothermal method were carried out. Surface properties of the synthesized nanomaterials were studied by Scanning Electron Microscopy, SEM, Atomic Force Microscopy, AFM, and X-ray Photoelectron Spectroscopy, XPS. X-ray diffraction, XRD and Raman spectroscopy were performed in order to determine phase composition. Impedance spectroscopy demonstrated the influence of nanoparticles on the electrical conductivity.

EXPERIMENTAL STUDIES AND THERMODYNAMIC CALCULATIONS OF STRUCTURAL AND PHASE COMPOSITION FOR Ti–Si–C SYSTEM AT HEAT TREATMENT

Thermodynamic calculations of structural and phase balance in the Ti–Si–C system at 1100–1400 °C was made using the CALPHAD method. The paper demonstrates the calculated phase diagrams of this system. It is found that 100 % of the Ti 3 SiC 2 phase is formed at the stoichiometric relationship of components. Deviations in the carbon or silicon content lead to the formation of titanium carbide, titanium disilicide, or silicon carbide in the system. The phase composition is virtually not affected by the temperature in the examined temperature range. The paper provides comparison of the calculated data with the experimentally determined phase composition of the said system samples after the spark plasma sintering of the mechanoactivated powder. In practice, the process temperature and the duration of high-temperature soak significantly affect the phase composition of the final product due to the limited speed of solid phase reactions during the synthesis of compounds. The resulting samples have a grain size of 1–5 μm and hardness of 4–15 GPa depending on the phase composition.

Hydrothermal Synthesis of Nanocrystalline Titanium Dioxide for Use as a Photoanode of DSSCs

Nanocrystalline TiO2powder was synthesized using microwave-assisted hydrothermal treatment of titanium oxysulfate in the presence of NH4F. X-ray powder diffraction analysis and Raman spectroscopy were used to determine phase composition and particle size of obtained titanium dioxide. The studies using methods of TEM and EDX spectroscopy have shown that synthesized TiO2powder is a promising functional material for fabrication of photoanode of dye-sensitized solar cells (DSSCs).

Electrochemical Characterization of Nickel-Phosphorus Based Coatings Containing Cobalt

The Ni-P, Ni-Co-P and Ni-P+Co coatings were obtained in galvanostatic conditions at the current density ofjdep= -200 mA cm-2. A stereoscopic microscope was used for surface morphology characterization of the coatings. The X-ray diffraction (XRD) method was used to determine phase composition of the coatings and the atomic absorption spectrometry (AAS) was applied to specify their chemical composition. The behavior of the obtained coatings was investigated in the process of hydrogen evolution reaction (HER) from 5 M KOH using steady-state polarization and electrochemical impedance spectroscopy (EIS) methods. It was found that introduction into Ni-P amorphous matrix powder of cobalt produced porous electrode materials which could be used for the HER.

Performance of rice husk ash blended cement concretes subjected to sulfate environment

This work assessed the performance of rice husk ash (RHA)-based ASTM type I and type V (low tricalcium aluminate (C3A)) blended cement concrete mixtures subjected to a mixed magnesium–sodium sulfate environment for an immersion period up to 48 months. The concrete mixtures comprised a combination of two Portland cements (type I and type V) and two RHA-blended cements with two water-to-binder ratios of 0·35 and 0·45. In addition to fresh and strength properties, X-ray diffraction, differential scanning calorimetry, mercury intrusion porosimetry and rapid chloride permeability tests were conducted on all concrete mixtures to determine phase composition, pozzolanic activity, porosity and chloride ion resistance. Deterioration of concrete due to mixed sulfate attack and corrosion of reinforcing steel were evaluated by assessing concrete weight loss and measuring corrosion potentials and polarisation resistance at periodic intervals throughout the immersion period of 48 months. Plain (type I/V) cement concretes performed better in terms of deterioration and corrosion resistance than RHA-based type I/V blended cement concrete mixtures in a mixed sulfate environment.

Solid solution or amorphous phase formation in TiZr-based ternary to quinternary multi-principal-element films

TiZr-based multicomponent metallic films composed of 3–5 constituents with almost equal atomic concentrations were prepared by co-sputtering of pure metallic targets in an Ar atmosphere. X-ray diffraction was employed to determine phase composition, crystalline structure, lattice parameters, texture and crystallite size of the deposited films.The deposited films exhibited only solid solution (fcc, bcc or hcp) or amorphous phases, no intermetallic components being detected. It was found that the hcp structure was stabilized by the presence of Hf or Y, bcc by Nb or Al and fcc by Cu. For the investigated films, the atomic size difference, mixing enthalpy, mixing entropy, Gibbs free energy of mixing and the electronegativity difference for solid solution and amorphous phases were calculated based on Miedema׳s approach of the regular solution model. It was shown that the atomic size difference and the ratio between the Gibbs free energies of mixing of the solid solution and amorphous phases were the most significant parameters controlling the film crystallinity.

High-pressure Sapphire Cell for Phase Equilibria Measurements of CO<sub>2</sub>/Organic/Water Systems

The high pressure sapphire cell apparatus was constructed to visually determine the composition of multiphase systems without physical sampling. Specifically, the sapphire cell enables visual data collection from multiple loadings to solve a set of material balances to precisely determine phase composition. Ternary phase diagrams can then be established to determine the proportion of each component in each phase at a given condition. In principle, any ternary system can be studied although ternary systems (gas-liquid-liquid) are the specific examples discussed herein. For instance, the ternary THF-Water-CO2 system was studied at 25 and 40 °C and is described herein. Of key importance, this technique does not require sampling. Circumventing the possible disturbance of the system equilibrium upon sampling, inherent measurement errors, and technical difficulties of physically sampling under pressure is a significant benefit of this technique. Perhaps as important, the sapphire cell also enables the direct visual observation of the phase behavior. In fact, as the CO2 pressure is increased, the homogeneous THF-Water solution phase splits at about 2 MPa. With this technique, it was possible to easily and clearly observe the cloud point and determine the composition of the newly formed phases as a function of pressure. The data acquired with the sapphire cell technique can be used for many applications. In our case, we measured swelling and composition for tunable solvents, like gas-expanded liquids, gas-expanded ionic liquids and Organic Aqueous Tunable Systems (OATS)(1-4). For the latest system, OATS, the high-pressure sapphire cell enabled the study of (1) phase behavior as a function of pressure and temperature, (2) composition of each phase (gas-liquid-liquid) as a function of pressure and temperature and (3) catalyst partitioning in the two liquid phases as a function of pressure and composition. Finally, the sapphire cell is an especially effective tool to gather accurate and reproducible measurements in a timely fashion.

Nickel-Cerium Alloys for Borohydride Oxidation

Nickel and nickel-cerium (Ni-Ce) alloys with different amounts of Ce (5 and 10 at.% Ce) have been prepared by arc melting and characterized by scanning electron microscopy and electron probe microanalysis based on energy dispersive X-ray spectroscopy, to investigate microstructure and to determine phase composition. Subsequently, Ni and Ni alloy-based electrodes were fabricated and studied for borohydride (BH4 -) oxidation in alkaline media by cyclic voltammetry and chronoamperometry in the temperature range 25 – 45 ºC. Preliminary results showed comparable BH4 - oxidation peak current densities obtained at three electrodes, with Ni95Ce5 electrode giving the highest current densities. Electrochemical data are modelled to obtain relevant kinetic parameters of BH4 - oxidation at these electrodes. Effect of electrolyte temperature on the evaluated parameters has been investigated as well.

Characterization of Alloys and Liquidus Projections of Ternary Bi-Sb-Sn system

AbstractGiven that Sn-based lead-free solders are considered as possible substitution for standard lead-tin solders, properties of the alloys from ternary Bi-Sb-Sn system were characterized by microstructural SEM-EDS analysis, Brinell hardness tests, and electrical conductivity measurements. Isothermal cross section at 298 K and liquidus surface projection were calculated by application of CALPHAD method and software package PANDAT 8.1. The experimentally determined phase compositions in analyzed microstructures were found to be in a good agreement with phases on calculated cross sections.

Studies on CO 2 decomposition over H 2-reduced MFe 2O 4 (M = Ni, Cu, Co, Zn)

Decomposition of CO 2 over reduced MFe 2O 4 (M = Ni, Co, Cu, Zn) was studied by H 2–TPR, H 2–TG, and CO 2–TG. XRD Rietveld analysis was used for determining phase composition and crystallite size of reduced and oxidized samples. The results indicate that spinel CoFe 2O 4 and CuFe 2O 4 are reduced to metals by H 2, while ZnFe 2O 4 and NiFe 2O 4 only partly reduced at 350 °C. The CoFe 2O 4 spinel ferrite shows the best activity in decomposing CO 2 and the ZnFe 2O 4 shows the best recovery ability in the process of redox.

Effect of Nano Silica on the Sinterability of Hydroxyapatite Dense Bodies

The effects of adding a small amount of nano silica in hydroxyapatite (HA) on the sinterability and mechanical properties of hydroxyapatite were studied. The starting HA powder was synthesized using a novel wet chemical precipitation method. Different amount of silica powder was mechanically mixed with the synthesized HA. The green samples were subsequently cold isostatically pressed at 200 MPa. Sintering in air was accomplished by firing the green samples at temperatures ranging from 1050°C to 1250°C. Sintered samples were analyzed to determine phase composition and mechanical properties. The XRD analysis revealed that with increasing the amount of silica in the HA powder, decomposition of HA to TCP occurred at sintering temperature higher than 1050°C. The bulk density of all silica-doped samples decreased through the temperature range studied. In agreement with the bulk density trend, the increasing silica additives in HA depleted the Young’s modulus and Vickers hardness of the HA body. The study revealed that the addition of silica have an adverse effect on the sintered properties of hydroxyapatite bioceramics.

Dielectric and relaxor behavior of BaBi 4Ti 4O 15 ceramics

Barium bismuth titanate BaBi 4Ti 4O 15 (BBiT) ceramics have been prepared using non-conventional solid-state reaction route based on mechanochemical synthesis during intensive milling. The X-ray diffraction method was used to determine phase composition. Dielectric properties were investigated in a wide range of temperatures (20–800 °C) and frequencies (1.21 kHz–1 MHz). The broad dielectric constant peaks at temperature T m is frequently dependent. A modified Curie–Weiss relationship is used to study the diffuseness behavior of a ferroelectric phase transition where value of γ indicates the degree of diffuseness of barium bismuth titanate ceramics. The dielectric relaxation rate follows the Vogel–Fulcher relation with E a = 0.013 eV, ν 0 = 2.09 × 10 8 Hz and T f = 651 K. All these parameters indicate that BaBi 4Ti 4O 15 is a relaxor ferroelectric. Ohmic conductivities and associated activation energies were evaluated using impedance spectroscopy.

Resistance of Scoria-Based Blended Cement Concrete against Deterioration and Corrosion in Mixed Sulfate Environment

The use of blended cements incorporating supplementary cementing materials and cements with low C3A content is becoming common to prevent the deterioration of concrete structures subjected to aggressive environments. This paper presents the results of an investigation on the performance of finely ground volcanic scoria (VS)-based ASTM Type I and Type V (low C3A) blended cement concrete mixtures with varying immersion periods of up to 48months in environments characterized by the presence of mixed magnesium–sodium sulfates. The concrete mixtures comprise a combination of two Portland cements (Types I and V) and two VS-based blended cements with two water-to-binder ratio of 0.35 and 0.45. Background experiments (in addition to strength and fresh properties) including X-ray diffraction (XRD), differential scanning calorimetry (DSC), mercury intrusion porosimetry (MIP), and rapid chloride permeability (RCP) were conducted on all concrete mixtures to determine phase composition, pozzolanic activity, porosity, and chloride ion resistance. Deterioration of concrete due to mixed sulfate attack and corrosion of reinforcing steel were evaluated by assessing concrete weight loss and measuring corrosion potentials and polarization resistance at periodic intervals throughout the immersion period of 48months. Plain (Type I/V) cement concretes, irrespective of their C3A content, performed better in terms of deterioration and corrosion resistance compared to Type I/V VS-based blended cement concrete mixtures in mixed sulfate environment.

The Effect of Sodium Dopants on Calcium Polyphosphate Biomaterials

Sodium-doped CPP was synthesized using three dopant sources (sodium carbonate, sodium hydroxide and sodium phosphate). These materials were analyzed by XRD to determine phase composition and by differential thermal analysis to identify phase transition temperatures. Sintering of resulting glass powders showed that both dopant source and dopant concentration affects sinter neck formation and crystallinity. The open porosity of sodium phosphate and sodium carbonate doped samples at 0.1 Na2O/CaO sintered at different temperatures changed significantly. Crystallization of the construct during sintering was noted at temperatures lower than expected.