Phase Texture Research Articles

Effect of end groups with aliphatic chain or ring structures on the thermal properties and optical textures of achiral and chiral liquid crystal compounds

Thermal properties and orientation in optical textures of liquid crystal (LC) are two crucial factors for LC application. Here, a series of achiral and chiral LC compounds (Cn) with different end groups were prepared. The chemical structures were investigated by Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (1H NMR). The thermal properties and optical textures were studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (XRD). The results showed that all the compounds possessed good thermal properties and enantiotropic mesomorphism. For achiral compounds C1C4, droplets and schlieren textures of nematic phase (N) and broken fan-shape textures and dull grayish/cloudy textures of smectic phase (Sc) were seen. Oily streak and focal conic textures of chiral nematic phase (N*), fan-shape textures and dull grayish/cloudy textures of chiral smectic phase (Sc*) were observed for chiral compounds C5C7. For C1, C2, C3 and C5 with aliphatic chain in the end groups, it was found that lateral substitution in the end groups had a greater effect on the clearing point than that of the increase in the length of end groups. Moreover, due to the increasing free volume for the increase of branch chain on six-membered ring structure, the clearing point (Ti) of C4 was higher than those of C6 and C7.

Development of foam-like emulsion phases in porous media flow

HypothesisWhile surfactant solutions mobilize residual oil under optimal conditions by lowering the water–oil interfacial tension, emulsion phases outside of the optimum tend to be immobile. How are mobility and texture of such phases related, and how can the stability of these phases be understood? Can non-optimized surfactant solutions improve displacement processes through mobility control? ExperimentEmulsification and miscibility during surfactant flooding were investigated in microfluidics with generic oil and surfactant solutions. The salt concentration was varied in an exceptionally wide range across the optimal displacement conditions. The resulting emulsion textures were characterized in situ by optical and fluorescence microscopy and ex situ visually and by Small-Angle X-ray Scattering. FindingsDuring displacement, oil is increasingly solubilized and transported in a phase with a foam-like texture that develops from a droplet traffic flow. The extent and stability of these emulsion phases depend on the salinity and surfactant efficiency. The similarity with textures of classic foam phases is used to hypothesize the mechanisms that stabilize such macroemulsions in porous media. The observed microscopic displacement mechanisms can be traced back to foam formation, quality and transport. The resulting phases are of particular interest for mobility control during surfactant flooding, which, however, requires further investigation.

Solidification texture, variant selection, and phase fraction in a spot-melt electron-beam powder bed fusion processed Ti-6Al-4V

The effect of a spot melt strategy on the solidification texture, variant selection, phase fraction, and their variations along the build height was investigated in comparison to a conventional linear melt strategy. Ti-6Al-4V alloy samples were manufactured by an electron-beam powder bed fusion process using two different melt strategies and characterized using high-energy synchrotron x-ray diffraction. The linear and spot melt cases resulted in β<100> cube and fiber textures, respectively, with the cube/fiber axis nearly parallel to the build direction. The α phase exhibited Burgers orientation relationship (BOR) with the parent β phase for both melt strategies. Although all of the key texture components and the BOR between the α and β phases were consistently observed in both cases along the build height, there were several measurable differences between the two. At the top of the build height, the β<100> build texture intensity was stronger in the linear case. However, the texture intensity in the linear case decreased gradually from the top to near the substrate, whereas the spot melt case did not show this trend. Moreover, the BOR was examined along the build height and the results showed that there is a distinct variant selection in the spot melt case, unlike the linear case. Specifically, the planar variants sharing ( 1 ̅ 01 ) β || ( 0002 ) α with [ 2 ̅ 2 ̅ 2 ̅ ] β and [ 2 2 ̅ 2 ] β were the most prominent in the spot melt, but no preference was identified in the directional variants. The β phase fraction was slightly lower in the spot melt case compared to the linear case. In both the cases, the β phase fraction decreased moving towards the substrate but remained significantly higher than that of the powder feedstock. Overall, the novel spot melt strategy produced a more homogeneous microstructure in terms of both the phase fraction and texture across the build height.

Effect of Tempering on the Phase Composition and Texture of the α and γ Phases in VNS9-Sh TRIP Steel

Effect of Tempering on the Phase Composition and Texture of the α and γ Phases in VNS9-Sh TRIP Steel

Importance of water content in birnessite-type MnO2 catalysts for HCHO oxidation: Mechanistic details and DFT analysis

Water is featured in an indispensable role during the process of catalytic oxidation of HCHO. In this work, a rich water-containing birnessite-type MnO2 was synthesized, and its water content was adjusted through calcination. Phase structure and texture properties of the prepared birnessite were characterized. It was revealed that three types of water (namely absorbed water, molecular water, and structural hydroxyl) existed in birnessite. With the loss of water content, the interlayer distance of samples had decreased which changed the structure of birnessite to cryptomelane. This converted the morphology from an initial layered shape to a rod-like shape. Besides, the underlying mechanism for this effect on HCHO catalytic oxidation was elucidated. Results indicated that hydroxyl groups could slowly and sequentially oxidize HCHO to DOM, formate, and carbonate species. The hydroxyl groups also promoted the formation of oxygen vacancy which could activate O2 to O− 2 and O−. The hydroxyl groups which were consumed had originally been supplied by the reaction between O- 2, O−, and H2O (absorbed and interlayer water in birnessite) which was then replenished from air stream. Clearly, water is favorable to the catalytic reaction. It is the main reason why birnessite can continuously decompose HCHO.

The effect of hydrolysis duration on the phase composition, texture, aggregation and agglomeration of ZrO2 nanoparticles

The effect of hydrolysis duration on the phase composition, texture, aggregation and agglomeration of ZrO2 nanoparticles

Effect of annealing temperature on microstructure, texture and tensile properties of TA32 sheet

The aim of this paper was to study effect of annealing temperature on microstructure, texture and tensile properties of a high temperature titanium alloy sheet. The as-received sheet exhibited an equiaxed structure consisting of primary α phase and few retained β phase. The α phase texture showed a typical B-type texture with <0001> inclined to normal direction. The intracrystalline substructure played an important role on tensile strength when the annealing temperature below 900 °C. Duplex microstructure with B + R-type texture was obtained when annealing temperature increased to α＋β region (900–990 °C). The intensity of B-type texture and R-type texture was found to be determined by the volume fraction of primary α phase and transformed β phase. Significant increase of tensile strength after α＋β region annealing was thought to result from the secondary α-β interfaces strengthening, and the formation of R-type texture lead to the anisotropy of tensile strength. Widmanstatten structure was obtained when the sheet suffered a β phase region annealing (1000–1020 °C) and the tensile strength decreased instantly.

Heat treatment of additively manufactured Ti-6Al-4V alloy: Microstructure and electrochemical properties

The effects of heat treatment on the microstructure of additively manufactured (AM) Ti-6Al-4V were investigated. The relationship between the microstructure characteristics and the surface activity of AM Ti-6Al-4V was explored. Electrochemical analysis results revealed that AM Ti-6Al-4V annealed at 940 °C exhibited a stronger ability to corrosion resistance, followed by an alloy cooled at 1020 °C. The Ti-6Al-4V alloy with aging treatment at 540 °C showed a higher corrosion rate. The difference in the corrosion rate of the specimens was obtained through corrosion experiment conducted using a 0.5 mol L–1 hydrochloric acid-hydrofluoric acid solution, and the results of the initial stage of immersion were consistent with the electrochemical measurements. Variations in the phase content and texture were the main factors affecting the corrosion resistance of Ti-6Al-4V. An increase in the β phase and a decrease in the α’ grains were beneficial to improving the corrosion resistance performance. Specimens with a higher< 110 >texture strength possessed preferable corrosion resistance under more than 2 days of immersion. The preferential growth of the oxide film in the direction of< 110 >//ND was considered a critical factor in improving the corrosion resistance of AM Ti-6Al-4V alloy.

Freezing and Thawing of D2O/Sand Mixtures Investigated by Neutron Diffraction

Evolution ice diffraction patterns in mixtures of D2O with quartz sand of three different grain coarseness (100–600, 300–800 and 600–1200 μm) were studied under various temperature regimes by means of neutron diffraction method. The studied structural parameters and characteristics involved the phase composition of specimens, Ih D2O ice lattice parameters, and crystallographic texture of the present phases. Variations in the ice crystallographic texture during the repeated freezing and thawing were observed for all tested sample types, showing an intermittent enhancement of ice and quartz texture indices accompanying the start of specimens cooling. Formation of radial internal stresses is demonstrated by the observed split of (002) and (100) diffraction maxima of ice. Estimated mean internal radial stress values are calculated.

Synthesis and study the liquid crystalline behaviors of double Schiff bases bearing ester linkage as a central core

ABSTRACT Two series of 12 homologues, 4-(((4-substituentphenyl)imino)methyl)phenyl 4-((4-(alkoxy) benzylidene)amino)benzoate (Dn, X = –OCH3 and En, X = –-Br), have been synthesised. The two series have different alkoxy terminal chains (OC n H2 n +1, n = 3, 4, 6, 7, 9, 12) on one side of their structures while other side in the series (Dn and En) was substituted by methoxy and Bromo group, respectively. The structures of the synthesised derivatives have been identified using Fourier transform infrared spectrometry (FT-IR) and nuclear magnetic resonance for H and C (1H-NMR, 13C-NMR) and the elemental analysis (CHN). The texture of liquid crystalline phases of the mesogens has been observed by optical polarised microscopy (OPM) while the details of the thermal transition of compounds were investigated by differential scanning calorimetry (DSC). The obtained liquid crystalline results showed that the derivatives of series (Dn) display a broad range of nematic mesophase (N) while the mesogens of (En) series appeared nematic and smectic mesophases. All the studied homologues show a wide range of liquid crystalline mesophases, the stability of mesomorphic behaviour of these compounds was dependent mainly on the length of terminal alkoxy chain (the number of carbon atoms) chain and the effect of substituent groups (OCH3 and Br).

STRUCTURE - PROPERTY - PROCESSING CORRELATIONS IN METASTABLE BETA TITANIUM ALLOYS Ti-10V-2Fe-3Al AND Ti-5Al-5Mo-5V-3Cr

ABSTRACT This paper describes the microstructure, texture and tensile properties of the two metastable β titanium alloys (Ti-10V-2Fe-3Al and Ti-5Al-5Mo-5V-3Cr). Both the alloys exhibit the single β (body centered cubic) phase in β solution treated and water quenched (β ST WQ) condition. The β ST WQ samples were aged at two different temperatures (550 and 750 °C) and different aging times (2, 4 and 6 hrs). The aging has resulted in different α phase morphologies of a phase precipitates. The sizes and volume fractions of the a phase increase and decrease with increase in aging temperature, respectively. The higher aging temperature (750 °C) results in precipitation free zones (PFZ) within the vicinity of prior β grain boundaries. The a phase texture is basal and it changes to non-basal with increase in aging time. The sharp a phase texture consists of {0001} || ND fibre with high intensity. The Vickers hardness values of both the alloys increase from β ST WQ to all aging temperatures due to precipitation hardening. The specimens aged at 550 °C have resulted in high strength in alloy Ti-1023. In contrast, 750 °C aged samples of both the alloys result in lower strength and moderate elongation values.

Polarization and Phase Textures in Lattice Plasmon Condensates.

Polarization textures of light may reflect fundamental phenomena, such as topological defects, and can be utilized in engineering light beams. They have been observed, for instance, in photonic crystal lasers and semiconductor polariton condensates. Here we demonstrate domain wall polarization textures in a plasmonic lattice Bose–Einstein condensate. A key ingredient of the textures is found to be a condensate phase that varies spatially in a nontrivial manner. The phase of the Bose–Einstein condensate is reconstructed from the real- and Fourier-space images using a phase retrieval algorithm. We introduce a simple theoretical model that captures the results and can be used for design of the polarization patterns and demonstrate that the textures can be optically switched. The results open new prospects for fundamental studies of non-equilibrium condensation and sources of polarization-structured beams.

Association of silica phases as geothermobarometer for eucrites: Implication for two‐stage thermal metamorphism in the eucritic crust

AbstractSilica mineral is present in different stable polymorphs depending on the temperature and pressure conditions of crystallization. We suggest using silica mineral phases to constrain the thermal history of eucrites. We focused on silica minerals in basaltic clasts of nine non‐cumulate eucrites to compare with previously studied cumulate eucrites. Our observations indicate an apparent relationship between thermal metamorphic degrees and silica phase texture in basaltic clasts of non‐cumulate eucrites. To reveal complex transformation relations between silica polymorphs in eucrites, we performed cooling experiments (cooling rate: 1 and 0.1 °C h−1) and heating experiments (heating 500 °C for 168 h and 800 °C for 96 h) using eucrites. The cooling experiments show that cristobalite is an initial silica phase crystallized from eucritic magma and transforms to quartz at the cooling rate between 0.1 and 1 °C h−1. Based on the cooling experiments and observations of eucrites, we suggest that a combination of silica minerals varies depending mainly on cooling rates. According to the heating experiments, monoclinic tridymite hardly transforms to other phases at low temperature by short reheating events such as brecciation. Monoclinic tridymite can partially transform to quartz with a “hackle” fracture. We conclude that a reheating event partially transformed monoclinic tridymite to quartz to form aggregates of monoclinic tridymite and quartz with the hackle fracture in eucrites. We suggested that some basaltic clasts in non‐cumulate eucrites experienced two‐stage thermal metamorphism in the eucritic crust. The first metamorphic event has resulted from burial under lava produced by successive eruptions. Igneous intrusions into the preformed crust may have caused the second metamorphic event. The intrusions heated the deep eucritic crust and induced the transformation from monoclinic tridymite to quartz.

Study on the Grain Boundary Misorientation Change and Texture Evolution in SUS304 Austenitic Stainless Steel at Low Cold‐Rolling Reductions

To study the grain boundary misorientation change and texture evolution in austenitic stainless steel at low cold‐rolling reductions, SUS304 austenitic stainless steel samples with a cold‐rolling reduction of 5%, 8%, 10%, 15%, 20%, and 23% are prepared. The electron backscatter diffraction analysis reveals that with the increase in the cold‐rolling reduction, the proportions of low‐angle grain boundary (LAGB) and high‐angle grain boundary (HAGB) gradually increase and decrease, respectively. The decrease in HAGB reduces the toughness of the material. With the increase in cold‐rolling reduction, the strain area inside the material increases, which enhances the toughness and strength of the steel plate. Austenite textures at different cold‐rolling reductions are composed of Brass, Goss, S, and shear texture {011}&lt;122&gt;. The intensity of the Brass‐type texture increases with the increasing cold‐rolling reduction. The martensite texture mainly consists of R‐Cube, Brass, shear texture {111}&lt;110&gt;, {111}&lt;112&gt;, and {332}&lt;113&gt;. When the cold‐rolling reduction is less than 15%, the Brass texture appears in the α′‐martensite phase. In addition, the intensity of the R‐Cube texture increases with the increasing cold‐rolling reduction. The martensite phase texture is affected by the austenite phase texture, and its formation can be attributed to the Kurdjumov–Sachs orientation relationship.

Structure, Optical and Electrical Properties of the High Doped ZnO Thin Films Deposited By RF Magnetron Sputtering of Powder Target in Methane Ambient

The ZnO thin films were deposited by RF-magnetron sputtering of ZnO powder target using pure argon, argon with hydrogen and argon with methane as reactive gas. Surface morphology and crystalline structure of the films were studied by SEM, XRD and XRR techniques. Chemical composition and optical properties were investigated by SIMS, Raman scattering spectroscopy (RSS), PL spectroscopy and spectral ellipsometry. Electrical measurements were performed on the ZnO films deposited on SiO2-Si and silicon wafers n- and p-type with Ni contacts by TLM, IV, CV characteristics, admittance spectroscopy, Van der Pauw and Hall methods. It was found that growth morphology, crystalline structure, optical and electrical properties of the films are strongly affected by adding methane to argon during the deposition process. Adding of methane resulted in a destruction of hexagonal phase texture and considerable increase a size of ZnO nanocrystallites (from 50 nm for argon to 200 nm for argon/methane working gas). SIMS measurements demonstrated that methane promoted hydrogen incorporation into the ZnO film that was more than an order of magnitude larger in comparison with adding molecular hydrogen in the gas mixture at the same concentration. Adding of methane resulted in a high energy shift of near band edge ultraviolet photoluminescence band, quenching of deep level emission in the visible spectral range and increase of optical band gap from 3.24 to 3.45 eV. The strongest effect of methane has been found for electrical resistivity that reduced by 3 orders of magnitude in comparison with films deposited in pure argon. Additionally, electrical conductance of the ZnO film deposited at high methane concentration does not depend on measurement temperature. Hall method with combination with Van der Pauw resistivity measurements shows: strong n-type doping of the film; donor concentration more than 1020 cm-3 slightly depending on methane concentration; maximum electron mobility about 7 cm2/V s. The direct comparison of resistivity and donor concentration of the films deposited using methane and molecular hydrogen as doping precursors has demonstrated that doping efficiency of methane is about an order of magnitude larger than that of molecular hydrogen under similar deposition conditions. On the other hand, methane addition in working gas resulted in an intensity decrease of the E2L (100 cm-1) and E2H (438 cm-1) lines in the RSS that can be associated with some disturbance of the ZnO structure. Additionally a peak at 71 cm-1 was observed in some films that can be related to the metallic Zn. The possible mechanisms of the ZnO film formation, nature of the doping and electron transport mechanisms will be discussed.

Facile synthesis of calcium magnesium zirconium phosphate adsorbents transformed into MZr4P6O24 (M: Ca, Mg) ceramic matrix for radionuclides immobilization

Calcium zirconium CaZr4P6O24 and magnesium zirconium MgZr4P6O24 phosphates with NZP structure are promising materials for the safe disposal of high radioactive wastes. Herein, firstly the facile synthesis of calcium magnesium zirconium phosphate adsorbents transformed into MZr4P6O24 (M: Ca, Mg) ceramic matrix as effective materials for radionuclides adsorption and immobilization was developed. The detailed analysis of phase composition, functional groups, elements content, surface morphology, texture and adsorption characteristics of prepared calcium magnesium zirconium phosphates were performed. It was shown that obtained samples were amorphous materials. The high efficacy (K d > 104cm3/g) of prepared adsorbents towards 137Cs, 85Sr, 60Co radionuclides in the wide pH range of 4.0–10.0 was demonstrated. The formation of calcium zirconium CaZr4P6O24 and magnesium zirconium MgZr4P6O24phosphates with zirconia ZrO2admixture during adsorbents calcination at 1000 °C was shown. The obtained results have high capabilities for the development of effective calcium magnesium zirconium phosphate adsorbents for radionuclides immobilization into MZr4P6O24(M: Ca, Mg) ceramic matrix.

Through-Thickness Microstructure Characterization in a Centrifugally Cast Austenitic Stainless Steel Nuclear Reactor Primary Loop Pipe Using Time-of-Flight Neutron Diffraction

The US code of Federal Regulations mandates regular inspection of centrifugally cast austenitic stainless steel pipe, commonly used in primary cooling loops in light-water nuclear power plants. These pipes typically have a wall thickness of ~8 cm. Unfortunately, inspection using conventional ultrasonic techniques is not reliable as the microstructure strongly attenuates ultrasonic waves. Work is ongoing to simulate the behavior of acoustic waves in this microstructure and ultimately develop an acoustic inspection method for reactor inspections. In order to account for elastic anisotropy in the material, the texture in the steel was measured as a function of radial distance though the pipe wall. Experiments were conducted on two 10 × 12.7 × 80 mm radial sections of a cast pipe using neutron diffraction scans of 2 mm slices using the HIPPO time-of-flight neutron diffractometer at the Los Alamos Neutron Science Center (LANSCE, Los Alamos, NM, USA). Strong textures dominated by a small number of austenite grains with their (100) direction aligned in the radial direction of the pipe were observed. ODF analysis indicated that up to 70% of the probed volume was occupied by just three single-grain orientations, consistent with grain sizes of almost 1 cm. Texture and phase fraction of both ferrite and austenite phases were measured along the length of the samples. These results will inform the development of a more robust diagnostic tool for regular inspection of this material.

Specific features of crystallographic texture formation in BCC-FCC transformation in extruded brass

Crystallographic features of body-centered cubic to face-centered cubic transformation were studied in an extruded brass product. X-ray phase analysis, scanning electron microscopy with electron microprobe analysis, and orientation microscopy based on diffraction of back-scattered electrons were used. A sample after treatment consisted of the β′-phase (Cu0.55Zn0.45, structural type B2) and α-phase (Cu0.65Zn0.35, structural type A1) at 30:70. Integral textures (within the product) of phases were axial with axes parallel to the elongation direction in extrusion:< 110 >for β’ and< 100 >for α. Local textures of phases are described as limited and consisting of a set of components. For β′ – {001}< 110 >, with scattering up to± 25° around the axis< 110 >; and {110}< 110 >consisting of three components – one {110}< 110 >and two {110} ± 24° around the axis< 110 >; for α – {001}< 100 >(strong) and two of {110}< 111 >(weak). It was shown that components of local textures of the β′- and α-phases were associated by orientation relationships close to Kurdjumov-Sachs orientation relationships. A small number of limited textural components formed as a result of β(BCC)→α(FCC) transformation realized as per multi-variant orientation relationships is explained by the formation of nuclei of a new phase at special boundaries close to coincidence site lattice boundaries Σ3 and Σ33.

Effect of Aging Temperature and Time on Secondary Phase Precipitation and Texture in an Ultrafine Grained 2205 Duplex Stainless Steel after Cold Rolling

Abstract The present work evaluates the precipitation of secondary phases in a cold-rolled ultrafine-grained 2205 duplex stainless steel after aging at temperatures ranging from 600°C to 950°C for different annealing times (300–86,400 s). X-ray diffraction, scanning electron microscopy coupled with electron backscattered diffraction, and transmission electron microscopy were used for microstructural characterization. Mechanical properties were evaluated using tensile and Vickers microhardness tests. σ- (sigma), χ- (chi), and chromium carbide (M23C6) phases were identified. σ- and austenite phase volume fractions increased with aging time, whereas χ-phase and carbides remained nearly constant, and the ferritic volume fraction decreased. Inverse pole figures of σ-phase, for a specimen aged at 850°C for 24 h, showed a localized distribution of orientations, normal to the rolling direction, being centered around the [001], whereas for the other annealing conditions, a concentration between the orientations [001] and [110] was observed. Although mechanical strength was increased, the ductility was reduced as the secondary phase precipitation proceeded.

Modeling of the synthesis conditions impact on the structure of calcium magnesium phosphates

Calcium magnesium phosphates are widely used as bioceramics, sorbents, catalysts, cement, etc. Herein, calcium magnesium phosphates were obtained by chemical precipitation from a solution using dolomite as a source of calcium and magnesium, hydroxyethylidene diphosphonic acid as an inhibitor of crystallization. The chemical composition of synthesized samples was characterized with a molar ratio (Ca + Mg)/P of 1.29–1.52 and Mg/(Mg + Ca) of 0.54–0.65. The effect of various parameters (solution temperature, precipitator addition rate, duration of precipitate aging, solution addition sequence, and method of precipitation washing) on the chemical and phase composition, texture, and morphology of calcium magnesium phosphates by X-ray diffraction, Fourier transform infra-red spectroscopy, differential-thermal and thermogravimetric analyses, N2 adsorption-desorption, scanning electron microscopy, and fractional factorial experiments were studied. It was established that (i) the hydroxyethylidene diphosphonic acid addition, (ii) the sequence of adding reaction solutions, and (iii) the method of precipitation washing had the greatest influence on the chemical and phase composition of the obtained samples. The surface area and pore volume of calcium magnesium phosphates were significantly increased by the introduction of hydroxyethylidene diphosphonic acid up to 265 m2/g and 0.568 cm3/g, which makes it possible to obtain materials with a developed mesoporous structure for adsorptions application.