Phase Properties Research Articles

Oil Viscosity Effects on Lithium 12-Hydroxystearate Grease Modulus and Thixotropy

Abstract The effect of base oil viscosity and temperature on thixotropic recovery of lubricating grease (LG) is investigated via shear rheology. The viscosity of the base lubricant phase of LGs impacts the storage modulus in both the undisturbed and post-sheared states. In this study, we focus on three greases with varied base oil viscosity but similar chemistry: Polyalphaolefin (PAO) 8, PAO 40, and PAO 100. Small amplitude oscillatory shear testing is first used to evaluate the viscoelastic modulus in the undisturbed state at varied temperature. A 1-hour full rotation shear is then applied to mechanically disrupt the LGs. The storage modulus is then tracked over time under varied temperature to investigate thixotropic recovery. These results show that the physical properties of the fluid phase of LGs can significantly impact the mechanical properties of the solid phase present in LGs and that the storage moduli is a function of state related to temperature.

NMR and MD Simulations of Non-Ionic Surfactants

Non-ionic surfactants are an important solvent in the field of green chemistry with tremendous application potential. Understanding their phase properties in bulk or in confined environments is of high commercial value. In recent years, the combination of molecular dynamics (MD) simulations with multinuclear solid-state NMR spectroscopy and calorimetric techniques has evolved into the most powerful tool for their investigation. Showing recent examples from our groups, the present review demonstrates the power and versatility of this approach, which can handle both small model-surfactants like octanol and large technical surfactants like technical polyethylene glycol (PEG) mixtures and reveals otherwise unobtainable knowledge about their phase behavior and the underlying molecular arrangements.

Mineral Plastics and Gels from Multi‐Arm Ionomers

AbstractPlastic production and waste are a growing menace that affects the soil, the marine environment, and the air in a cumulative manner. The demand for mineral and bioplastics from renewable and biodegradable materials has therefore increased in all relevant sectors. The use of currently available degradable plastics is, however, limited by their poor mechanical properties and high production costs. In addition, many of today's plastics undergo uncontrolled biodegradation processes that involve harsh or expensive conditions and which may last from months to years. Here, the advantages of using multi‐arm polymers for the production of sustainable mineral plastics are presented. A 4‐arm poly(acrylic acid) is synthesized via atom transfer radical polymerization and is reacted with divalent calcium ions to obtain semi‐liquid hydrogel or degradable plastic when dried. The mechanical properties of the different phases are evaluated and compared with linear poly(acrylic acid) of the same molecular weight. The multi‐arm approach yielded improved mechanical characteristics, including self‐healing and biodegradation without compromising other typical hydrogel characteristics. This concept of synthesizing multi‐arm polymers with improved characteristics from building blocks of traditionally linear structures may be applicable to other mineral and bioplastic materials including acrylates, polysaccharides, and DNA.

Conjugated core-shell bottlebrush polymers that exhibit crystallization-driven self-assembly.

Bottlebrush polymers are complex architectures with densely grafted polymer side chains along polymeric backbones. The dense and conformationally extended chains in bottlebrush polymers give rise to unique properties, including low chain entanglement, low critical aggregation concentrations, and elastomeric properties in the bulk phase. Conjugated polymers have garnered attention as lightweight, processible, and flexible semi-conducting materials. They are promising candidates in electronic devices and sensors, but their optoelectronic properties depend on adequate polymer ordering, π-π interactions, and crystallization. Crystallization-driven self-assembly of conjugated polymers has become a prominent method to optimize properties including band energies, redox potentials, and exciton diffusion and transport. Much progress has been made in controlled block copolymer self-assembly, but despite their promising properties, reports of conjugated bottlebrushes have been limited, and their self-assembly is relatively unexplored. For the first time, we report the synthesis of conjugated core-shell bottlebrush polymers. These materials contain poly(3-hexylthiophene) (P3HT) and poly(ethylene glycol) (PEG) in either core or shell position. We demonstrate that the use of P3HT as a crystallizable conjugated polymer and PEG as a colloidally stabilizing and disaggregating block facilitates their self-assembly into a number of unique crystalline morphologies with longer conjugation lengths and lower exciton bandwidths relative to analogous diblock copolymers. These include intramolecularly self-assembled segregated bottlebrush polymers, short nanofibers formed by end-on-end stacking of bottlebrush molecules, extremely long >20 μm nanofibers formed exclusively by end-on-end stacking, and >15 μm nanoribbons formed from both end-on-end and side-by-side stacking of bottlebrush polymers.

MODELING OF WATER-OIL FLOW IN SHALE POROUS STRUCTURES: EFFECT OF WETTABILITY AND CAPILLARY NUMBERS

Shale oil reservoirs are characterized by dense, extremely low permeability, and poorly developed natural fractures. Hydraulic fracturing technology is often used in extraction to improve recovery. It is important to clarify the mechanism and influence mechanism of displacement in complex porous media coupled with fractures and matrix to enhance oil recovery. In this study, based on the lattice Boltzmann method (LBM) utilizing the fracture-matrix pore coupling model, the authors carried out a study of displacement in organic and inorganic pore space. They systematically investigated the influence mechanisms of wettability and capillary numbers on the oil recovery rate. It was found that the stronger the wettability of the water phase, the higher the oil recovery rate, the lower the residual oil in the form of adsorbed oil film, the larger the capillary numbers, and the higher the oil recovery rate. Oil in organic pore space is more difficult to discharge compared with that in inorganic pore space, and the recovery rate of oil in organic pore space can be effectively improved by increasing the driving pressure and enhancing the properties of the water phase (fracturing fluid).

Selective laser melted Ti particle modified AlSi10Mg composite: Microstructure, strengthening phase, and mechanical properties

Selective laser melted Ti particle modified AlSi10Mg composite: Microstructure, strengthening phase, and mechanical properties

Enhanced photocatalytic performance of polyaniline nanoparticles for efficient dye degradation under simulated sunlight.

This study investigates the effectiveness of polyaniline oxide (PANI) nanoparticles as photocatalysts for the degradation of organic dyes under visible light irradiation. Known for their stability and adjustable conductivity, PANI nanoparticles were synthesized via a hydrothermal method using P123 surfactants, followed by calcination. The morphology, structural phase, and optical properties of the synthesized PANI materials were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). Results indicated that the synthesized PANI nanoparticles agglomerated into spherical particles with an average size of 70-80 nm. The photocatalytic properties of PANI materials were evaluated by the decolorization of rhodamine B (RhB) and methylene blue (MB) under simulated sunlight irradiation. The PANI photocatalyst was found to be highly effective in removing MB dye, achieving a removal efficiency of approximately 97.09% with a rate constant of 2.08 × 10-2 min-1. In comparison, the removal efficiency for RhB was about 58.01%. Additionally, the mechanism behind the photocatalytic degradation of MB dye by PANI was investigated and discussed. The study highlights the photostability and reproducibility of PANI nanoparticles through recycling experiments, contributing to the development of sustainable photocatalytic materials for efficient water treatment.

Effect of Si powder on the phase composition, microstructure and properties of MgAl2O4-SiC composite materials

Effect of Si powder on the phase composition, microstructure and properties of MgAl2O4-SiC composite materials

Investigation of the relation between surfactant head group size and formation of different types of lyotropic structures in two surfactants/dye systems

Lyotropic phase properties of novel mixtures of some dodecylalkylammonium bromide surfactants (DAABr) in the mixtures of 1-dodecanol (DDeOH)/Sunset Yellow dye (SSY)/water were investigated. DAABr surfactants were chosen as dodecyldimethylammonium bromide (DDMABr), dodecyldimethylethylamonium bromide (DDMEABr) and dodecyltriethylammonium bromide (DTEABr). In lyotropic mixtures, both surfactants were used in the mixtures, i.e., DDMABr/DDMEABr and DDMEABr/DTEABr to control the average number of the methylene (−CH2) groups in their head groups (navg) at the aggregates’ surfaces. By changing the relative concentrations of each surfactant in the mixtures at constant total surfactant and mixture compositions, lyotropic mixtures presenting lamellar, nematic, and hexagonal phases were obtained. The textures and types of lyotropic phases were analyzed by polarizing optical microscopy (POM), also confirmed by Small-angle X-ray scattering data. Uniaxial-to-biaxial nematic phase transitions were determined from the temperature dependence of the birefringences via laser conoscopy. Temperature-navg partial phase diagrams of the mixtures were constructed by combining the POM and laser conoscopy results. Small-angle X-ray scattering (SAXS) was performed to determine the structural parameters. The results indicate that there is a close relation between the stabilization of different lyotropic structures and the average size per surfactant head group (a0) and the navg values.

Preparation of glass-ceramics via co-sintering of coal fly ash and metastable slag

ABSTRACT Coal fly ash (CFA) was used as the main object of study to prepare ash microcrystalline glass by co-sintering with metastable slag (MS) using its strong crystallization ability and sintering activity at low and medium temperatures. The effects of different material ratios on the crystalline phase composition and properties of the microcrystalline glass were discussed using various physical and chemical analysis methods in combination with mechanical properties tests. The results show that the compressive strength, density, chemical resistance and sintering densities of ash microcrystalline glass gradually increase with the increase of sintering temperature and the proportion of metastable slag. The compressive strength of the prepared ash microcrystalline glass can meet the requirements of GB/T19766–2016 “Natural Marble Building Panel” (≥50 MPa) when the addition amount of fly ash is 10–40% and the sintering temperature is 850–1085°C; among them, the chemical corrosion resistance of the prepared product meets the industrial requirements when the addition amount of fly ash is 10–30% and the sintering temperature is 940°C (acid loss rate ≤ 96%, alkali loss rate ≤ 98%).

Bubble Plume Behavior and Turbulence Characteristics of Gas–Liquid Phase in Power‐Law Fluids

AbstractThe turbulent characteristics of bubble plumes in power‐law fluids are studied by experiments and numerical simulations. The effects of liquid phase rheological properties and superficial gas velocity on liquid phase velocity, shear stress, turbulent kinetic energy, turbulent scale, and gas holdup of the bubble plume are investigated. The velocity, shear stress, and turbulent kinetic energy of the liquid phase are distributed in a circular pattern during the generation stage, forming stage, and free‐surface interaction stage of the bubble plume. The average shear stress and average turbulence kinetic energy that decomposed turbulent scales in CMC aqueous solution are 31–50 times and 1.4–2 times than that in tap water environment. The gas holdup in the flow field decreases with the increase of concentration of liquid phase and increases with the increase of superficial gas velocity. The flow pattern of the bubble plume is significantly affected by the superficial gas velocity and the rheological properties of the liquid phase that affect the transfer of mass and momentum between phases.

Lasing in Crystals Based on 7‐Azaindole‐Phenylhydrazone Organoboron Compounds

AbstractThe development of efficient organic solid‐state lasers requires an in‐depth understanding between chemical structure, intermolecular interactions in the crystal phase, and optical and electronic properties. This study highlights these closed dependencies in novel 7‐azaindole phenylhydrazone derivatives and their corresponding boron complexes, by deploying a combined approach of experimental techniques and theoretical calculations (Density Functional Theory and Time‐Dependent Density Functional Theory) in the solvated and solid‐state phase. Notably, it is found that when these compounds, which are weakly emissive in solution, are processed into crystalline microfibers, they experience a sharp emission enhancement and exhibit laser action at low pump fluence thresholds. This is achieved by partially inhibiting structural relaxation, which drives non‐radiative decay, a critical factor for effective lasing, highlighting the potential of these materials for future optoelectronic applications.

Influence of Sintering Temperature on Microstructure and Dielectric Properties of Strontium Calcium Titanate (Sr<sub>0.9</sub>Ca<sub>0.1</sub>TiO<sub>3</sub>) Ceramics

Strontium Calcium Titanate (Sr0.9Ca0.1TiO3) ceramic powders were synthesised using a solid sintering technique and were uniaxially pressed and sintered at different temperatures of 1100 °C, 1150 °C, 1200 °C, 1250 °C, and 1300 °C for three hours. Physical, phase, microstructure and dielectric properties were studied. Perovskite Cubic Strontium Calcium Titanate phase was crystallized. With an increase in sintering temperature, the density and grain size of Sr0.9Ca0.1TiO3 ceramics increased. Grain boundaries were observed in the microstructure of Sr0.9Ca0.1TiO3 sintered at higher temperatures. At room temperature, the dielectric constant and dielectric loss are observed to increase with the increase in sintering temperature. AC conductivity enhanced with sintering temperature.

Superlattice Thermal Modulation in MoS2${\rm MoS}{_2}$ by Defect Engineering

Abstract is one of the most investigated and promising transition‐metal dichalcogenides. Its popularity stems from the interesting properties of the monolayer phase, which can serve as the fundamental block for numerous applications. In this paper, an atomistic perspective on the modulation of thermal transport properties in monolayer through strategic defect engineering, specifically the introduction of sulfur vacancies is proposed. Using a combination of molecular dynamics simulations and lattice dynamics calculations, how various distributions of sulfur vacancies (ranging from random to periodically arranged configurations) affect its thermal conductivity is shown. Notably, it is observed that certain periodic arrangements restore the thermal conductivity of the pristine system, due to a minimized interaction between acoustic and optical phonons facilitated by the imposed superperiodicity. This research deepens the understanding of phononic heat transport in two‐dimensional (2D) materials and introduces a different point‐of‐view for phonon engineering in nanoscale devices, offering a pathway to enhance device performance and longevity through tailored thermal management strategies.

Structural, dielectric, optical and photocatalytic properties of (Na0.5Bi0.5)ZrO3 lead-free perovskite: insights from experimental and ab initio theoretical studies

Abstract In this work, we present structural, dielectric, optical and photocatalytic properties of the room temperature phase of the lead-free perovskite (Na0.5Bi0.5)ZrO3 (NBZ) system. The structural and optical properties are analyzed by combining a first-principles density functional theoretical approach and experimental characterizations. A conventional solid-state method is used for the synthesis process. X-ray powder diffraction and Rietveld refinement of the powder patterns at room temperature showed the NBZ material to be orthorhombic perovskite belonging to the space group Pnma. The calculated lattice constants of NBZ are found to be in good agreement with the experimental results. The dielectric study revealed a diffuse phase transition (DPT) in the vicinity of 290 °C. Based on the microscopic composition fluctuation model and phenomenological theory, a reasonable and effective characterizing parameter, the diffuseness degree, of the DPT is defined. The bandgap energy is estimated using UV–Vis spectroscopy and the optical absorption spectrum. The photocatalytic performance evaluation is performed by investigating the photodegradation kinetics of different pollutants by NBZ under visible light irradiation. The highest degradation efficiency is achieved for methylene blue (MB) dye (99% within 180 min), followed by rhodamine B (RhB), Congo red (CR) and methyl orange (MO) dyes. Overall, our results suggest good efficiency for NBZ as a photocatalytic agent with implications for large-scale photocatalytic applications in environmental and energy concerns. Furthermore, our study also provides several important benchmarking results on NBZ that have not been reported so far.

Enhanced Mechanical Properties Via the Incorporation of Ti in Cu Alloys

The influence of Ti addition on the microstructure, mechanical properties and electrical conductivity of Cu-14Fe alloy is studied. Great emphasis has been laid on the second phase, texture and mechanical properties. No new phase other than α-Fe phase could be found in Cu-14Fe-0.1Ti alloy using XRD and SEM. With 0.1Ti addition, the distribution of α-Fe phase strip is slightly heterogeneous. Cube, s and brass texture components are largely strengthened in Cu matrix with Ti addition, while copper and goss texture components are rare in Cu matrix of both alloys. In α-Fe phases, α fiber and goss texture components are highly strengthened with Ti addition. It is found that enhanced mechanical properties are achieved in Cu-14Fe-0.1Ti alloy. In detail, with Ti addition, the yield strength and ultimate tension strength increase from 538 and 561 MPa to 580 and 583 MPa, respectively, while maintaining a high value of elongation to failure (6.5%). A lower equivalent grain size and a higher KAM value mainly contributes to the higher yield strengthening effect in Cu-14Fe-0.1Ti alloy. The lower equivalent grain size is derived from the small size distribution range and the small size of Cu matrix in Cu-14Fe-0.1Ti alloy. The dissolution of Ti and formation of nano second phases also improve mechanical properties. However, texture hardly plays a role in the strengthening effect. 0.1Ti addition hardly reduces the electrical conductivity of Cu-14Fe alloy, maintaining a value of 33.43% IACS. The results in this work could provide guidance in texture evolution and property evaluation in Cu-Fe alloys.

Numerical Study on Heat Leakage, Thermal Stratification, and Self-Pressurization Characteristics in Liquid Helium Storage Tanks

During the operation of liquid-phase He-4 (LHe-4) storage tanks, heat leakage changes the thermophysical parameters and phase properties of the LHe-4 in the tanks, resulting in the thermal layering phenomenon. This phenomenon is characterized by the LHe-4 temperature gradient and pressure increase (self-pressurization) phenomena in the tanks. Based on the Layer-by-Layer model, a heat transfer model of a composite adiabatic structure with multilayer insulation and liquid nitrogen screen (LNCS) insulation was established, and the Neumann boundary heat flux of the thermal response model was determined. A numerical simulation model of the thermal response of a liquid helium storage tank was established. The spatial and temporal evolutions of the pressure distribution, natural convection characteristics, thermal stratification characteristics, and self-pressurization characteristics of the LHe-4 tank were investigated. Finally, the self-pressurization thermodynamic model of the LHe-4 storage tank was built based on the isothermal saturation and homogeneous model. It is shown that the predictive performance of the mLee model for the self-boosting characteristics (relative deviation of 14.32%) was significantly improved compared with that of the Lee model (relative deviation of 39.64%). The thermal stratification degree (TSD) of the tank increased with the operation time, with TSDs of 1.023, 1.028, and 1.036 at 1 h, 2 h, and 3 h, which exacerbated the self-pressurization of the tank. The wall surface in contact with the phase interface is a strong evaporation point, so the interfacial mass transfer rate maps show a pattern of high at both ends and low in the middle.

Microstructure and Mechanical Properties of 28 % High Chromium White Cast Iron

The chemical composition of the metal and carbide phase, hardness, and common mechanical properties of cast iron, ICH28H2 cast iron, a type of high-chromium white cast iron, and the dependence of hardening, annealing, and tempering process types were studied. Therefore, annealing and hardening heat treatments were employed, and the results were compared to measurements in the as-cast state. The metal matrix exhibited content within the range of 16.8% to 19.7% Cr and 71.9% to 76% Fe, while the carbide phase showed 63.4% to 64.7% Cr and 23% to 24.8% Fe. The Cr carbide in high Cr white iron primarily appeared as (Fe, Cr)7C3 type, leading to the calculated chemical formula of the eutectic carbide as (Fe2Cr5)C3. The as-cast white iron displayed a hardness of 53 HRC, which increased marginally to 56.2 HRC after hardening. This suggests that the 28% Cr white iron alloy does not exhibit a significant hardness enhancement compared to the cast state, attributed to its high Cr content. The hardness of the metal phase directly influences the overall hardness change of the alloy, while the carbide hardness is dependent on its Cr content. Abrasive wear studies revealed that 28% Cr white cast iron exhibited superior wear resistance in the as-cast state compared to the hardened state, aligning with research indicating that cast iron demonstrates optimal wear resistance in its cast state.

Numerical investigation on circular interference photoelectron momentum distributions induced by spatiotemporal optical vortex pulse

Using the strong field approximation theory, we conducted a detailed numerical investigation on the photoelectron momentum distributions (PMDs) arising from the ionization of hydrogen atoms by a circularly polarized spatiotemporal optical vortex (STOV) pulse. STOV pulses have a unique spatial structure and peculiar phase properties. Our simulations reveal that PMDs exhibit a complex interference structure characterized by circular momentum bands intertwined with intricate interference fringes. A thorough examination of the multi-photon process provides a comprehensive explanation for the circular momentum band formation. We develop an expression to elucidate their center momentum positions within the PMDs. Furthermore, we perform a detailed analysis of the fine interference fringes, attributing their origin to the singular phase of the STOV pulse. Despite their distinct manifestations, we infer that the circular momentum bands and fine interference fringes stem from the simultaneous dependence upon the space and time variables of the STOV phase.

Influence of high‐iron bauxite on phase composition, microstructure, and properties of bauxite‐based homogenized grogs

AbstractInvestigation on the occurrence state of Fe2O3 in bauxite and its effect on the bauxite‐based homogenized grogs (BHG) is crucial for the utilization of high‐iron bauxite resources. BHG with different Fe2O3 contents incorporated in the form of high‐iron bauxite was prepared by maintaining the Al2O3 content around 82%. The effect of high‐iron bauxite addition (0, 25, 50 75, 100 wt.%) on the phase composition and microstructure evolution was studied using X‐ray diffractometer, scanning electron microscope, and Factsage software. The results show that part of the Fe2O3 in BHG is dissolved into crystalline phases, while the other part is present as a glass phase. The addition of high‐iron bauxite, coupled with a reduction in the SiO2 content, results in a rise in the corundum content within BHG from 55.0% to 93.6% and a decrease in the mullite content from 44.0% to 2.8%. This change results in a decline in the refractoriness under load of T0.6, dropping from 1593.5°C in the sample without high‐iron bauxite to 1430.7°C in the sample with 100% high‐iron bauxite addition. The microstructure of BHG evolves from the interconnected network of corundum and mullite phases to the structure of corundum bonded by the glass phase.