Changes In Phase Composition Research Articles

Determination of eight phosphatidylethanol homologues in blood by reversed phase liquid chromatography–tandem mass spectrometry – How to avoid co-elution of phosphatidylethanols and unwanted phospholipids

Phosphatidylethanols (PEths) are specific, direct alcohol biomarkers with a substantially longer half-life than ethanol, and can be used to distinguish between heavy- and social drinking. More than forty PEth homologues have been detected in blood from heavy drinkers, and PEth 16:0/18:1 is the predominant one. Since PEths are phospholipids it can be difficult to isolate them from unwanted phospholipids during sample preparation. To minimize possible matrix effects it is therefore important to separate PEths from other phospholipids during LC-MS/MS analysis. In this study, we have investigated how the retention and chromatographic separation of eight PEth homologues and the phospholipid background are influenced by changes in mobile phase composition using two different LC columns, the Acquity BEH C18 column (50 × 2.1 mm ID, 1.7 µm particles) and the Kinetex biphenyl column (100 × 2.1 mm ID, 1.7 µm particles). Our findings show that the buffer concentration of the aqueous part of the mobile phase had a huge effect on the retention of PEth homologues and separation of PEths from unwanted phospholipids. By using a buffer-free mobile phase consisting of 0.025% ammonia in Type 1 water, pH 10.7, as solvent A and methanol as solvent B, all eight PEth homologues were separated from both the early eluting lyso-phospholipids and the later eluting phospholipids with two fatty chains using the BEH C18 column. The knowledge obtained in this study can be of great importance for those seeking to develop reliable and robust bioanalytical LC-MS/MS methods for determination of PEth homologues.

Investigation of the necessity to apply a (Ce, Gd)O2 interlayer between the low-temperature processed (La, Sr)CoO3 electrode film and the (Zr, Y)O2 electrolyte in solid oxide fuel cells

Gadolinia doped ceria (GDC) interlayers have been widely used to avoid resistive phase formation at the mixed ionic electronic conductor (MIEC) (La,Sr)CoO3 (LSC) air electrode/ yttria stabilized zirconia (YSZ) electrolyte interfaces. Although MIEC electrodes fabricated by low-temperature metal organic precursor methods offer the highest electrochemical performance, no studies exist on the effect of GDC interlayer on their performance. In this work, we investigated the necessity for a GDC interlayer between the low-temperature processed LSC electrode and the YSZ electrolyte. Through x-ray diffraction, scanning transmission electron microscopy/energy-dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy analyses, we studied the impact of the GDC interlayer on i) the formation of resistive zirconate phases at the LSC/YSZ interface and ii) the overall phase and surface chemistry evolution. While no resistive zirconate phases formed in the LSC/YSZ system due to low processing temperatures, La leaching into the GDC layer altered the overall phase evolution, in addition to the resulting cation stoichiometry. This LSC/GDC/YSZ system showed a polarization resistance improved by an order of magnitude, attributable to the changes in phase composition.

Enhanced de-/hydrogenation kinetics of a hyper-eutectic Mg85Ni15-Ag alloy facilitated by Ag dissolving in Mg2Ni

In order to accelerate the hydrogen absorption and desorption rates of hyper-eutectic Mg-Ni alloy, Mg 85 Ni 15- x Ag x ( x = 0, 0.2, 0.4, 0.6) alloys were prepared and the results show that fishbone eutectic was formed without change of phase composition. It was found that Ag atoms were dissolved in fishbone eutectic Mg 2 Ni and the average cell parameters of Mg 2 Ni increase with the increase of Ag content. Owing to adjusting lattice parameters, the hydrogen absorption and desorption rates of Mg 85 Ni 14.8 Ag 0.2 alloy are significantly improved. About 4.47 wt% hydrogen is absorbed at 275 ℃ only in 1 min, with the maximum capacity of 5.84 wt% in 60 min. The Mg 85 Ni 15- x Ag x ( x = 0.2, 0.4, 0.6) hydrides can be completely dehydrogenated within 10 min at 275 ℃. The corresponding activation energies for dehydrogenation are determined to be 80.4, 97.1 and 97.8 kJ/mol, respectively, which are lower than 117.8 kJ/mol of Mg 85 Ni 15 . The onset dehydrogenation temperature of Mg 85 Ni 14.8 Ag 0.2 hydride is reduced to 201 ℃, which is much lower than 220 ℃ of the Mg 85 Ni 15 hydride. The dissolving of Ag in Mg 2 Ni leads to a lattice expansion, which facilitates the diffusion for hydrogen atoms and decrease the energy barrier required for nucleation of Mg/Mg 2 Ni. As a result, the hydrogen de-/absorption rates were obvious accelerated and the onset dehydrogenation temperature was decreased. • The lattice size of Mg2Ni was regulated by doping Ag. • Hydrogen storage capacity of Mg85Ni14.8Ag0.2 alloy reaches 5.84 wt% at 275 ℃. • The Ea value for decomposition of Mg85Ni14.8Ag0.2 hydride decreases to 80.4 kJ/mol. • Addition of Ag reduces the initial desorption temperature of Mg85Ni15 hydrides.

Features of Changes in the Surface Structure and Phase Composition of the of α + β Titanium Alloy after Electromechanical and Thermal Treatment

Changes of structure, phase composition and microhardness in high-strength α + β titanium alloy were investigated after electromechanical treatment (EMT) and subsequent aging. The EMT was performed with alternating current density (j of 300 and 600 A/mm2). The aging was performed upon heating at 600 °C and exposure for 14 h. Methods of scanning electron microscopy, X-ray phase structure, micro X-ray spectral and durometric analyses were used. Modified layers (up to 200–250 µm in depth) on the surface of α + β titanium alloy were formed due to intensive thermo-deformation during the EMT and the following aging. The structure of the surface layer was characterized by high dispersivity (with particle sizes of about 30–500 nm), significant concentration heterogeneity (due to redistribution of the alloying elements and changes in the volume ratio of α- and β-phases), distortions in the crystal structure, increased levels of microstrain and microstress (2–2.5 times as compared to the initial) and increases in microhardness (by 30–40%).

Corrosion Performance and Mechanical Strength in Aluminum 6061 Joints by Pulsed Gas Metal Arc Welding.

In this paper, the analysis of electrochemical corrosion performance and mechanical strength of weld joints of aluminum 6061 in two-heat treatment conditions was performed. The joints were produced by gas metal arc welding in pulsed mode. The original material exhibited precipitates of and ” phases in a volume fraction (Vf) of 2.35%. When it was subjected to a solubilization process, these phases were present in a Vf = 2.97%. This increase is due to their change in shape and distribution in clusters within the aluminum matrix. After the welding process, the best sample in the solubilization condition reached 117 MPa, while the original material achieved 104 MPa, but all samples showed a fracture in the fusion zone. This is attributed to the heat input that produces high and low hardness zones along the heat-affected zone and the welding zone, respectively. Moreover, the change in microstructure and phase composition creates a galvanic couple, susceptible to electrochemical corrosion, which is more evident in the heat-affected zone than in the other weld regions, exhibiting uniform and localized corrosion, as was evident by electrochemical impedance spectroscopy. The heat from the welding process negatively affects the corrosion resistance, mainly in the heat-affected zone.

Numerical Approximation of the Nonequilibrium Model of Gradient Elution Chromatography Considering Linear and Nonlinear Solvent Strength Models.

In both linear and nonlinear chromatography, the lumped kinetic model is a suitable model for predicting elution bands when appropriate equilibrium functions and mass transfer coefficients are accessible. This model also works well in the case of gradient elution chromatography if variations in the equilibrium functions due to changes in the mobile phase composition are known. The rational selection of an optimum gradient is explored in this study from three different perspectives using the lumped kinetic model. Elution profiles generated by using (a) linear solvent strength, (b) quadratic solvent strength, and (c) power law are investigated. The effectiveness and reliability of the suggested numerical approach, utilizing the flux-limiting finite volume method, are demonstrated through numerical simulations. The impacts of axial dispersion, nonlinearity coefficient, Henry’s constant, mass transfer coefficient, and gradient parameters are studied on single and two-component elution profiles.

Effect of hydromagnesite on the hydration of hydratable alumina and properties of corundum-based castables

Hydratable alumina (HA) was premixed with hydromagnesite (BMC) to investigate the BMC impact on the hydration behavior of HA and the thermo-mechanical properties of HA bonded (HAB) castables. The phase composition, microstructure and mass changes of dried HA samples, were characterized by XRD, SEM, and TG, respectively. Flow ability, microstructure, and thermo-mechanical properties of HAB castables were studied. Results indicated that BMC effectively lowered HA hydration rate due to the decreased specific surface area. The hot modulus of rupture strength of castables was improved because the sintering of Al2O3 was enhanced by the MgO from BMC decomposition.

High discharge energy density and ultralow dielectric loss in alkali-free niobate-based glass-ceramics by composition optimization

The SrO-BaO-Nb2O5-SiO2 glass-ceramics with different (Sr, Ba)/Nb ratio were prepared by the melting-crystallized process. With the decrease of (Sr, Ba)/Nb, the bonding species and crystallization activation energy of the glass-ceramics were changed obviously, which caused the change of phase compositions and microstructures on a microscopic scale and the fluctuations of dielectric constant and breakdown strength on a macroscopic scale. Finally, the theoretical energy storage density was up to 18.93 J/cm3 with a dielectric constant of 84 and breakdown strength of 2256.73 kV/cm. What is more, the dielectric loss was less than 0.004 at room temperature. Furthermore, under the electric field of 640 kV/cm the discharge energy density of the optimal sample (S5) reached 1.14 J/cm3 which overtopped what has been reported and the discharge time (t0.9) was less than 16 ns. Above analysis suggested that the alkali-free niobate-based glass-ceramics have broad application prospects.

Evaluation of the Effect of High-Speed Sintering and Specimen Thickness on the Properties of 5 mol% Yttria-Stabilized Dental Zirconia Sintered Bodies

High-speed sintering of zirconia has become essential to single-visit dental prosthetic treatments. This important prosthetic dentistry technique demands a translucent material tougher than porcelain. Previous studies on high-speed sintered zirconia did not take heat and material thickness into consideration. We evaluated pre-sintered specimen thickness and the effect of high-speed sintering on the properties of 5 mol% Y2O3-stabilized zirconia (5Y zirconia). High-speed sintered bodies of 5Y zirconia were evaluated by density measurements, translucency measurements, three-point flexural and fracture toughness tests, X-ray diffraction (XRD), and scanning electron microscopy (SEM). High-speed sintering reduced the translucency and mechanical properties of 5Y zirconia. XRD and SEM observation results clarified that these reductions were due to the change in crystal phase composition and to the increase in residual pores, respectively, both resulting from high-speed sintering. Moreover, in high-speed sintering, as the thickness of the specimen increased, the number and size of internal pores increased, and the translucency and strength decreased. The threshold value for avoiding a reduction in translucency and mechanical properties was found to lie at ~4.4 mm. From the above results, it was concluded that 5Y zirconia is not suitable for high-speed sintering applications.

Effect of defects in laser selective melting of Ti-6Al-4V alloy on microstructure and mechanical properties after heat treatment

In this paper, the selective laser melting (SLM) Ti-6Al-4V sample with defects is heat treated (HT). The heat treatment temperatures are 750 °C, 850 °C, and 950 °C. The three temperatures are kept for 2 h, and then air cooling (AC) is used for treatment. Observe the changes in microstructure, phase composition, hardness, and tensile properties. The results show that the existence of defects will not affect the overall change trend of the microstructure, hardness and phase composition of the Ti-6Al-4V sample after heat treatment. However, there are obvious changes in the surrounding of two kinds of defects, which are the surface defects with large area and the lack of fusion (LOF) defects that are communicated with the outside world and extend to the inside of the sample. These two types of defects water, oil and air are easy to enter, and the defects are not easy to remove, heating will produce a large amount of hydrogen. Hydrogen enters the sample through defects, resulting in a large number of β phase around the two types of defects, and white around the defects. The hardness near the defect decreased significantly, and the closer the distance, the more the hardness decreased. A large amount of hydrogen entered into the Ti-6Al-4V sample, resulting in the appearance of new phase δ phase in the phase composition, resulting in the decrease of tensile strength（TS）and yield strength (YS) of the tensile properties after heat treatment, and the obvious decrease of elongation (EL). Moreover, among the various defects, the most important influence on the phase composition and tensile properties is the LOF defect that communicates with the outside world and extends to the inside of the sample.

Insight of BaCe0.5Fe0.5O3- δ twin perovskite oxide composite for solid oxide electrochemical cells.

One-pot synthesized twin perovskite oxide composite of BaCe0.5Fe0.5O3- δ (BCF), comprising cubic and orthorhombic perovskite phases, shows triple-conducting properties for promising solid oxide electrochemical cells. Phase composition evolution of BCF under various conditions was systematically investigated, revealing that the cubic perovskite phase could be fully/partially reduced into the orthorhombic phase under certain conditions. The reduction happened between the two phases at the interface, leading to the microstructure change. As a result, the corresponding apparent conducting properties also changed due to the difference between predominant conduction properties for each phase. Based on the revealed phase composition, microstructure, and electrochemical properties changes, a deep understanding of BCF's application in different conditions (oxidizing atmospheres, reducing/oxidizing gradients, cathodic conditions, and anodic conditions) was achieved. Triple-conducting property (H+/O2-/e-), fast open-circuit voltage response (∼16-∼470mV) for gradients change, and improved single-cell performance (∼31% lower polarization resistance at 600°C) were comprehensively demonstrated. Besides, the performance was analyzed under anodic conditions, which showed that the microstructure and phase change significantly affected the anodic behavior.

Fracture toughness and cracking behavior of frozen sandstone at different freezing temperatures

Fracture toughness and crack behavior of frozen rocks have an important guiding significance for engineering in cold regions, where the freezing temperature is one of the main factors that affect the mechanical properties of frozen rocks. Therefore, both mechanical properties (fracture toughness, compressive strength, and tensile strength) and pore phase composition of water-saturated sandstone at different freezing temperatures (0 °C, −2 °C, −4 °C, −6 °C, −8 °C, −10 °C, −12 °C, −15 °C, −20 °C) were tested in this paper. High-speed photography was used to capture the crack propagation process of the semi-circular bending (SCB) specimen. Also, morphological characteristics of the fracture surface under different freezing temperatures were analyzed. The results show the following: (1) The fracture toughness of saturated sandstone increases exponentially with the decrease of freezing temperature, reaching an increase of 402 % at −20 °C. (2) When the freezing temperature decreases from 0 °C to −8 °C, the crack growth rate increases rapidly. (3) The fracture surface roughness coefficient (Rs) of the SCB specimen shows a two-stage decreasing trend: a rapid decrease (0 °C to −8 °C), and a slow decrease (−8 °C to −20 °C). (4) The change of phase composition with freezing displayed two distinct stages: the unfrozen water content decreases rapidly and the ice content increases rapidly (0 °C to −4 °C) and then the unfrozen water content decreases slowly and the ice content increases slowly (−4 °C to −20 °C). Based on the above test results, we suggest that: (1) With the decrease of the freezing temperature, the pore phase composition changes significantly, resulting in enhanced mechanical properties of the rock. (2) The cementation and filling effect of pore ice reduce the dissipative energy in the process of crack expansion, increasing the brittleness index, so the crack growth rate of the SCB specimens increases rapidly.

Thermal Conductivity Model Analysis of Unsaturated Ice-Containing Soil

In cold locales, the thermal conductivity of soil porous media varies according to their composition and the phase state of the substance contained within the pore space. During the winter, water and other media in the soil pore space freeze-thaw, resulting in their phase state, composition, distribution, and significant thermal conductivity changes. There are some shortcomings in the current research regarding the thermal conductivity change pattern of unsaturated ice-containing soils. In this paper, the representative elementary volume (REV) selection method is given for unsaturated ice-containing soil with porosity as a representative state variable. Under the condition of freeze-thaw, two thermal conductivity REV analysis models for unsaturated ice-containing soil are established: a simplified volume-weighted average REV model and a fine volume-weighted average REV model; accordingly, a macroscopic thermal conductivity analysis model is given. The computational analysis is carried out with an actual unsaturated ice-containing soil example. The influence of the application of frozen soil in China is examined for its effect on the variation law of the thermal conductivity of porous medium. The variation characteristics of thermal conductivity of permafrost soil with related parameters (porosity, water ratio, moisture percentage, ice content, and tortuosity) are discussed. The model built in this paper provides novel concepts and methods for analyzing the thermal conductivity characteristics of unsaturated soil, as well as enhancing and advancing the analysis.

Laser Boronizing of Additively Manufactured 18Ni-300 Maraging Steel Part Surface.

The problem of insufficient wear resistance of maraging steels (MSt) has so far been solved mainly by the use of the thermochemical nitriding process, which has a number of limitations and disadvantages. In the present work, for MSt parts manufactured by laser powder bed fusion (LPBF), a more flexible laser alloying process was suggested as an alternative surface hardening process. The purpose of the present work is to give a better understanding on the possible hardening effect obtainable when amorphous boron is used as an alloying additive in relation with microstructural evolution and specific process parameters and to promote further development of this technology. For the alloying, a one kilowatt CO2 laser was applied at 0.5–4.0 mm laser spot and 250–1500 mm/min laser operating speed, providing 50,955–796 W∙cm−2 power density and 24.0–4.0 J∙mm−1 heat input. Before laser processing, surfaces were covered with amorphous boron. The appropriate melt pool geometry was obtained at 0.5 mm laser spot, for which XPS analysis revealed an increase in boron concentration from ~3.1 to ~5.7 wt.% with a laser speed increase from 500 to 1500 mm/min. XRD analysis revealed domination of Fe3B type borides along with the presence of FeB, Fe2B, Ni4B3 borides, austenitic and martensitic phases. The microstructure of modified layers exhibited evolution from hypoeutectic microstructure, having ~630–780 HK0.5 hardness, to superfine lamellar nanoeutectic (~1000–1030 HK0.2) and further to submicron-sized dendritic boride structure (~1770 HK0.2). Aging of laser-boronized layers resulted in the change of phase composition and microstructure, which is mainly expressed in a plenty precipitation of Mo2B5 borides and leads to a reduction in hardness—more significant (by ~200–300 HK0.2) for hypoeutectic and hypereutectic layers and insignificant (by ~50 HK0.2) for near-eutectic. With the application of the laser boronizing technique, the hardness of MSt parts surface was increased up to ~three times before aging and up to ~2.3 times after aging, as compared with the hardness of aged MST part.

Influence of liquid accelerator based on sodium aluminate on the early hydration of cement, C3A and C3S pastes

The objective of this study was to explore the influence of an alkali liquid accelerator based on sodium aluminate (ASa) on the early hydration behaviour of cement paste, tricalcium aluminate (C3A) and tricalcium silicate (C3S) and identify its accelerating mechanism. The setting times and mechanical properties of cement paste and mortar mixed with different amounts of ASa were determined. Isothermal calorimetry showed that the addition of ASa increased the first exothermic peak of cement hydration and advanced the second exothermic peak. The morphology of hydration products was analysed by scanning electron microscopy (SEM) and a model for the early hydration of cement paste was established. X-ray diffraction and SEM were also used to analyse the phase composition and morphology changes of C3A and C3S with or without ASa and early hydration models were established. Analysis of the experimental results revealed that the sodium hydroxide produced by ASa hydrolysis had the function of consuming gypsum, breaking calcium silicate hydrate gel film and increasing the calcium hydroxide concentration in the cement paste. The ettringite in the hydration products interweaved together to form a skeleton structure, which was conducive to cement paste hardening.

Low MOCVD growth temperature controlled phase transition of Ga2O3 films for ultraviolet sensing

The influences of low growth temperatures (420–490 °C) on phase transition of Ga2O3 films grown on Al2O3 substrates by means of metal-organic chemical vapor deposition (MOCVD) are investigated here. The changes of crystal structure, phase composition, surface and cross-sectional morphologies are carried out by X-ray diffraction, atomic force microscope and field-emission scanning electron microscope to reveal the detail evolution from ε-phase to β-phase in Ga2O3 films. The fluctuant Gibbs free energy change relying on growth temperature induces different growth mechanism of Ga2O3 films. Furthermore, the ultraviolet photoresponse properties of different phase compositions for Ga2O3 films are compared by constructing metal-semiconductor-metal photodetectors. It is found that mixture phase Ga2O3 films express better photodetection performance than pure phase Ga2O3 films due to the formation of built-in field within phase junction. This proposed regulation principle of Ga2O3 phase transition provides a new route to high-performance photoelectric material.

Method development and validation for simultaneous estimation of aspirin, ramipril and atorvastatin by RP-HPLC method in its pure and tablet dosage form

A simple, accurate, and precise method for estimating Aspirin, Atorvastatin, and Ramipril in Tablet dosage form was developed. Symmetry C18 (150 x 4.6 mm, 3.5) was used to run the chromatogram. At a flow rate of 1.0 ml/min, a mobile phase containing potassium dihydrogen ortho phosphate (pH adjusted to 3) and Methanol in the ratio 35:65 was pumped through the column. The temperature was kept at 30°C. The optimised wavelength chosen was 240.0 nm. Ramipril, Atorvastatin, and Aspirin had retention times of 1.803 minutes, 2.506 minutes, and 3.875 minutes, respectively. The percent RSD of Ramipril, Atorvastatin, and Aspirin were determined to be 0.99, 0.42, and 0.42, respectively. The method is linear for Ramipril concentrations ranging from 12.5 to 62.5 g/ml, Atorvastatin concentrations ranging from 160 to 800 g/ml, and Aspirin concentrations ranging from 5 to 25 g/ml. The method was accurate, with a percent recovery of 99.13 to 100 percent for Ramipril, 99.3 to 100.2 percent for Atorvastatin, and 99.3 to 100 percent for Ramipril, respectively. The developed method is robust after deliberate changes in flowrate and mobile phase composition with a percent RSD less than 2.

Influence of microstructure of composite amorphous/nanocrystalline Fe72Ni8Si10B10 alloy on the corrosion behavior in various environments

Thermal analysis of the composite amorphous/nanocrystalline Fe72Ni8Si10B10 alloy, in correlation with the XRD analysis of its individual sides, shows that the changes in phase composition induced by thermal treatment are followed by changes in microstructural parameters of the already present or newly formed phases in the alloy. These changes influence the corrosion behavior of the alloy in 0.5 M NaOH, NaCl and HCl solutions, according to the potentiodynamic polarization and EIS measurements. Beside the phase composition, the microstructure including crystal orientation and the state of the alloy surface is observed to have a significant role in the overall corrosion behavior.

Development of Technology for Processing Pyrite Cinder to Produce Non-Ferrous Metal Concentrate

The existing technologies for processing of pyrite cinder require improvement for complex extraction of non-ferrous, precious metals and iron. The novelty of the technology used in the work for the processing of pyrite cinders is the preliminary chemical activation in a solution of sodium bicarbonate. The optimal activation modes were determined according to temperature, duration, L:S ratio and NaHCO3 concentration. It has been established that activation of pyrite cinder results in changes in phase composition and a reduction in the content of the impurity components P2O5, SO3 and As2O3. The leaching of pyrite cinder after pre-activation in 15 % H2SO4 solution resulted in an extraction into solution, wt. %: CuO 76, 8; ZnO 75, 9 and Fe2O3 26, 0. The degree of extraction of non-ferrous metals in sulphuric acid solution without chemical activation is lower by 15 - 20 %.

Investigation of retention behavior of natural cannabinoids on differently substituted polysaccharide-based chiral stationary phases under reversed-phase liquid chromatographic conditions

The growing popularity of cannabis products and recent legalization of cannabis for recreational purposes have contributed to the increase of the demand for analytical methods able to give a detailed characterization of cannabis samples and derivatives. In this context, one of the aspects that is strongly emerging is about the hazardous potential of uncharacterised minor cannabinoids, including chiral ones, for which achiral potency testing methods currently employed do not give any information. For this reason, there is a growing interest towards the development of liquid chromatographic methods for the enantioseparation of cannabinoids. Much work is needed in this field where one of the major limitations is the lack of optically pure standards. This manuscript reports about the chromatographic behavior of five popular cannabinoids (including the cannabichromene racemate, CBC) on nine immobilised polysaccharide-based chiral stationary phases (CSPs) differently substituted, under reversed phase conditions. Results showed that chemo-selectivity of CSPs is not affected by changes in mobile phase composition, in the range of mobile phase investigated. In addition, the presence of electron withdrawing groups on the CSPs systematically leads to shorter retention times compared to when electron donating groups are present. An application of separation of cannabinoids from a real hemp extract on two of the chiral columns employed in this work revealed the presence of both CBC enantiomers in the sample.