Solid-liquid Phase Research Articles

Development and analysis of a powder bed friction stir (PBFS) additive manufacturing process for aluminum alloys: A study on friction-stirring pitch (ω/v) and print location

Metallic components fabricated with powder bed fusion additive manufacturing (AM) processes are known to have defects arising from liquid-solid phase transformation. Friction stirring can be an effective alternative source of heat, as evidenced in some of the recently developed powder deposition-based solid-state AM processes. However, they possess practical issues such as making compacted powder feedstock beforehand, consolidation of powder filler inside the tool during deposition followed by necessary extrusion, and significant flash formation, among a few. This paper proposed a novel powder bed friction stir (PBFS) additive manufacturing process inside a specifically designed mould that could potentially mitigate such issues in the existing technologies. The process was successfully demonstrated by building single-track and parallel double-track 3D structures layer-by-layer from an AA6061 powder bed using a rotating non-consumable friction stirring tool. Furthermore, for a better understanding of the underlying process mechanics, deposits were analyzed for their surface topography, microstructural evolution, and mechanical performance under different heat inputs as well as different print locations. Different heat inputs were applied by varying the friction-stirring pitch (FS pitch) from ‘Low’ to ‘High’. The print locations analysis was carried out in a parallel double-track fabricated at the optimal FS pitch. The results revealed that the ‘High’ FS pitch yielded an increased percentage of recrystallized grains and a fraction of high-angle grain boundaries as well as a larger average grain size due to the high heat input, better material intermixing, and the dominance of continuous dynamic recrystallization. As a result, an improved mechanical performance, except for the microhardness, was observed. The ‘High’ FS pitch also exhibited an improved surface topography. The results also revealed that the relative dominance of the re-stirring-induced recrystallization and the reheating-induced plastic deformation was the key factor for the variation of the microstructure in the longitudinal, transverse, and short-transverse directions. A gradual decrease in the tensile strength was observed from the ‘Top’ to the ‘Bottom’ segments of the overlapped region, contrary to the central region of a track.

A phase transition approach to elucidate the propagation of shear waves in viscoelastic materials

In the field of acoustics, a medium has traditionally been considered a liquid if shear waves cannot propagate. For more complex liquids, such as those containing polymer chains or surfactant aggregates, this definition begins to be unclear. By adopting a rheological model-independent approach, this work investigated by means of dynamic elastography, the liquid–solid phase transitions in viscoelastic liquid media. When the storage shear modulus G′ dominated the loss shear modulus G″, a minimal shear wave attenuation frequency region was defined and the medium was considered solid. When G″ dominated G′, the shear waves were strongly attenuated and the medium was considered liquid. The investigated medium, an aqueous solution of xanthan gum, behaved as a bandpass filter with transition bands, showing liquid–solid–liquid behavior from low to high frequency. During these transitions bands, shear waves still propagated but highly attenuated. The limiting values where shear waves were no longer observed were identified as the low and high cutoff frequencies. Finally, the ability of various rheological models to predict the phase transition frequencies and describe the dispersion curves was tested. A three-element rheological model, the Jeffreys model, was required to accurately fit the experimental response of the medium at different concentrations over the entire frequency range. Shear wave propagation methods can overcome the technical limitations of traditional rheometry and explore higher frequencies, rarely investigated in viscoelastic liquids.

LC-MS/MS quantification of vitamin K1 after simple precipitation of protein from low volume of serum

Quantification of vitamin K1 in serum is still quite a challenge for most analytical laboratories. For long, protein precipitation (PP) coupled with liquid–liquid extraction (LLE) or solid phase extraction (SPE) is the only choice for sample preparation before LC-MS/MS analysis. The objective of this study is to establish a novel method for the simple and rapid quantification of K1. To this end, three issues are illuminated in the first place: (i) the release efficiency of K1 is influenced by the type of precipitator and the volume ratio of serum to precipitator during PP; (ii) the absolute recovery of K1 will be compromised by the partition effect during extraction; (iii) the volume of injected serum per run should be proper rather than high to prevent the potential ion suppression effect. Benefitting from these findings, a single-step PP method is developed for K1 quantification for the first time. For pretreatment, isopropanol (100 μL), instead of the frequently used methanol, ethanol and acetonitrile, is utilized to release K1 from serum (25 μL), which realize the excellent release efficiency (>90%) and dilution effect (1:4) simultaneously. After validation, the method can provide favorable accuracy (91.5–112.2%) and precision (less than13.5%) in the wide concentration range (0.1–2.5 ng/mL). As a result, such method may provide a feasible and high-throughput alternative for evaluating K1 status in practice.

Control of chemical and microbial pollutants in liquid-solid phases of sewer pipes by Fe(II)-activated persulfate: Performance and mechanism of simultaneous removal

Most of the problems such as odor and corrosion in sewage systems originate from the biochemical reactions of liquid and solid phases in the pipes. Suppressing the activity of microorganisms and biofilms in the sewers is conducive to maintaining the proper operation of the sewer system. This study verified the removal of microorganisms and sulfides from wastewater and the inhibition of biofilm activity by peroxodisulfate (PDS) with the activation of ferrous ions (Fe(II)). Fe(II)/PDS can achieve efficient microbial inactivation within a reaction time of 20 min after a single dosing (Up to 95% removal of planktonic bacteria in the liquid phase), and the sulfide reduction can be maintained for more than 5 days, providing the possibility of intermittent dosing. The sulfide concentration can be maintained below 4 mg/L by intermittent dosing (average dosing interval is 10 days) during the long-term operation of the reactor. Dissolved organic matter (DOM) changes in sewage predict biofilm destruction. Changes in the biofilm microscopic morphology, extracellular polymer substances (EPS) fraction, biofilm functional groups, and microbial community revealed the effects of Fe(II)/PDS on the solid–liquid phase material fraction and biofilm structure of the sewage pipeline. The mechanism of biofilm disruption was analyzed based on the identification of strongly oxidizing active species in the Fe(II)/PDS system. This study shows that it is feasible to develop an efficient and cost-effective sulfide and microbial control strategy using Fe(II) with PDS in sewage systems.

Synergistic catalysis of MoS2-Ni3S2 heterojunctions to accelerate polysulfide conversion for high-performance Li-S battery

The sluggish conversion kinetics of polysulfides and its unprevented dissolution will lead to loss of active sulfur and act as the biggest obstacle for the widespread use of lithium-sulfur (Li-S) batteries. However, it is a great challenge to simultaneously response to the above-mentioned multiple requirements by the adoption of single catalyst. Herein, by incorporating the merits of strong adsorption and high electron conductivity of Ni3S2 with good catalytic of MoS2, a self-supported heterojunction MoS2-Ni3S2 catalyst has been developed with uniform rod-like morphology, which can provide larger specific surface area, better compensation of electrons, more effective catalysis, and faster solid phase transformation compare to its single component catalyst. Theoretical calculations and mechanism analyses suggest that the heterojunctions exhibit a synergistic process of “adsorption-diffusion-conversion” for polysulfides (LiPSs) and effectively facilitate the liquid-solid phase conversion(Li2S6→Li2S2/Li2S). Integrating the merits of Ni3S2 and MoS2, MoS2-Ni3S2 heterojunctions catalytic cathode deliver a good cycling stability with 70 % capacity retention after 150 cycles at 0.2 C with a high sulfur loading of 5.0 mg cm−2. Therefore, this work proposed a feasible catalyst design of bi-metal sulfides heterostructure which can simultaneously meet multiple kinetics requirements of Li-S system.

Experimental study on the change of coal structure and microbial community structure during supercritical-CO2-H2O-microorganisms-coal interaction process

To study the effects on coal structure and microbial community diversity during CO2 storage in deep unminable water-bearing coal seams, the lignite in the mining area of Inner Mongolia was selected as the research object. The simulation experiments of supercritical-CO2 (ScCO2)-H2O-microbial-coal interaction under different pressure conditions performed by using an autoclave. Then the solid–liquid phases before and after the reaction were analysed by XPS, low-temperature liquid nitrogen adsorption, 16S rRNA and other testing methods. The results showed that CO2 injection caused the pH and OD600 values in the system to decrease, and the pH and OD600 values in the system decreased more obviously with the increase of ScCO2 pressure. Compared with raw coal, the relative content of carbon elements on the surface of the coal after the reaction increased, and the organic carbon (CC/CH) relative content decreased slightly. In contract, the specific surface area, total pore volume, and the pore size of micropores of coal increased, but the average pore size of the mesopores and macropores decreased. At the same time, with the ScCO2 injection under different pressure conditions, some bacterial cells in the system ruptured and inactivated, resulting in the decrease their relative abundance. In contract, some genera, such as Paraclostridium and Methanoculleus, may have the adaptability to the extreme environment and gradually evolve into the dominant genus. In conclusion, the results provide a theoretical basis for studying the changes of ScCO2 on coal structure and microbial community structure during CO2 storage in deep unminable water-bearing coal seams.

Determination of 18 caine anesthetics in animal meat using solid phase extraction combined with ultra-performance liquid chromatography-tandem mass spectrometry

Because of the widespread application of anesthetic drugs in the fields of animal breeding and transportation, demand for the rapid, sensitive detection of anesthetic drugs in animal meat is increasing. The complex animal meat matrix contains various interfering substances, such as proteins, fats, and phospholipids, along with anesthetic drug residues at very low concentrations. Therefore, adopting appropriate pretreatment methods is necessary to improve the sensitivity of detection. In this study, a rapid, accurate analytical method based on ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and solid phase extraction (SPE) was established to determine the contents of 18 caines in animal meat. The MS parameters, such as the collision energies of 18 caines, were optimized. Furthermore, the chromatographic separation conditions and response intensities of the caine in different mobile phases were compared. The effects of different pretreatment conditions on the extraction efficiencies of the 18 caines in meat samples and those of different purification conditions, such as extraction solvent, SPE column, and dimethylsulfoxide (DMSO) dosage, on their recoveries were investigated. Combined with the external standard method, the 18 caines in meat were successfully quantified. Sample pretreatment is a three-step process. First, in ultrasound-assisted extraction, 2.0 g samples were added to 2.0 mL water and extracted using 10 mL 0.1% (v/v) formic acid in acetonitrile under ultrasound conditions for 10 min. SPE was then performed using an Oasis PRIME HLB column. Finally, DMSO-assisted concentration was employed: the organic layer was collected and dried at 40 ℃ under a stream of N2 gas with the addition of 100 μL DMSO. Acetonitrile-water (1∶9, v/v) was added to the residue to yield a final volume of 1.0 mL for use in UPLC-MS/MS. The 18 caines were separated using an HSS T3 (100 mm×2.1 mm, 1.8 μm) column with 0.1% (v/v) formic acid in water (containing 0.02 mmol/L ammonium acetate) and methanol as mobile phases. Samples were detected using an electrospray ion source (ESI) in the positive ion and multiple reaction monitoring (MRM) modes during UPLC-MS/MS. Under the optimized conditions, the 18 target caine anesthetics displayed good linearities in the range of 1.00-50.0 μg/L, and the correlation coefficients (R2) were >0.999. The respective limits of detection (LODs) and quantification (LOQs) were 0.2-0.5 μg/kg, and 0.6-1.5 μg/kg. In pork, beef, and mutton samples, the recoveries obtained at three spiked levels were 83.4%-100.4% with relative standard deviations (RSDs) of 3.1%-8.5%. This simple, rapid, sensitive method may be applied in the detection of 18 caine anesthetics in animal meat and may provide technical support to the food safety department in China in monitoring the residues of caine anesthetics in animal meat.

Modelling the solid–liquid–vapour phase behaviour of n-alkanes in a TPT-1 framework

We study the global phase behaviour of n-alkanes applying Wertheim's first order thermodynamic perturbation theory (TPT1). The molecules are modelled as homonuclear chains comprised of m freely jointed spherical segments interacting via the Lennard-Jones potential. Vega et al. [J. Chem. Phys. 116, 17 (2002)] have shown that the TPT1 is suitable to treat solid phases as well as fluid phases when model chains are considered, but that the adoption of a fully flexible chain model leads to the under-prediction of triple point temperatures and overestimation of the fluid ranges in comparison to experiment. Here, we propose a model in which a different number of segments are used to treat the fluid and the solid phase. The number of segments used to model the molecules in the fluid phase , and the LJ monomer potential parameters σ and ε are taken from published soft-SAFT values, whereas in the case of the solid phase a reduced temperature-dependent effective chain length is determined through a minimisation between theoretical and experimental liquid-solid phase equilibrium data. We refer to this model as effective-solid TPT1 (es-TPT1). We use the model proposed to calculate the solid–liquid–vapour phase diagrams of several n-alkanes and compare with experimental data. In the approach proposed, the conformation of chains in the solid phase is decoupled from the fluid phase, and an excellent description of the melting properties, as well as accurate predictions of the triple point temperatures for the n-alkanes examined is obtained. This simple solution provides an avenue to model the solid–liquid–vapour phase behaviour of other real substances in a TPT1 framework, and hence within the SAFT family of equations.

Small Molecules, Great Powers: Chemistry of Small Organo‐Chalcogenide Molecules in Rechargeable Li‐Sulfur Batteries

AbstractSmall organic chalcogenides molecules are receiving more attention in conjunction with the development of rechargeable lithium metal batteries (LMBs) especially lithium–sulfur (Li−S) batteries due to their abundant resources, reversible redox, high capacities, tunable structures, unique functional adjustability, and strong interaction with congener polysulfides. In this review, the working principles are generalized of small organo‐chalcogenide molecules in three important parts of batteries: electrolyte, interface, and cathode. First, in terms of regulating kinetics in electrolyte, small organo‐chalcogenide molecules can not only act as redox mediator to accelerate the redox kinetics of sulfur, but also change the inherently slow solid–solid process to form a faster redox pathway, which will bring light to the development of cryogenic Li−S batteries. Second, for interface chemistry, the introduction of small organo‐chalcogenide molecules can construct more elastic and stable anodic single‐SEI or cathodic/anodic dual‐SEI, thus effectively improving the cycling stability of batteries. Third, small organo‐chalcogenide molecules can be used as cathode materials in the form of liquid phase, solid phase, or precursor of polymers. Finally, advised optimizations are proposed about further mechanism deciphering, battery configuration design, machine learning, thereby providing direction to bridge the gap between rational modulation and practical battery implementation for small organo‐chalcogenide molecules.

Synthesis, X-ray Crystal Structure, Anticancer, Hirshfeld Surface Analysis, DFT, TD-DFT, ADMET, and Molecular Docking of 3-Phenyl-1,2,4-triazolo[3,4-h]-13,4-thiaza-11-crown-4

In this work, we describe the synthesis of new macrocycles derived from 3-phenyl-1,2,4-triazole-5-thione 1 in a heterogeneous medium using liquid-solid phase transfer catalysis (PTC) conditions. The structures of the two compounds (3 and 4) isolated were elucidated based on spectral data (1H-NMR, 13C-NMR) and confirmed in the case of 3-phenyl-1,2,4-triazolo [3,4-h]-13,4--thiaza-11-crown-4 (3) by a single-crystal X-ray diffraction analysis. Furthermore, the experimental spectral and the X-ray geometrical parameters were compared with their corresponding predicted ones obtained at the B3LYP/6-311++G(d,p) level of theory. The intercontacts between crystal units were investigated through Hirshfeld surface analysis. The drug-like macrocycles were predicted using ADMET and drug-likeness properties, which showed that 3 may act as an inhibitor of DNA-dependent protein kinase (DNA-PK). This assumption was confirmed by the well-binding fitting of 3 into the binding site of DNA-PK and the formation of a stable 3-DNA-PK complex with a binding energy of -7 kcal-mol-1. Finally, the anticancer activity of 3 was assessed by an MTT assay against A549 cells, which showed that 3 has moderate anticancer activity compared to that of the doxorubicin reference drug.

Integrating Fly Ash-Controlled Surface Morphology and Candle Grease Coating: Access to Highly Hydrophobic Poly (L-lactic Acid) Composite for Anti-Icing Application

New ways of recycling fly ash are of great significance for reducing the environmental pollution. In this work, biodegradable hydrophobic poly (L-lactic acid)/fly ash composites for anti-icing application were successfully fabricated via a facile solvent-volatilization-induced phase separation approach. A silane coupling agent of 3-(Trimethoxysilyl) propyl methacrylate was used to decorate a fly ash surface (FA@KH570) for strengthening the interface bonding between fly ash and poly (L-lactic acid). Moreover, FA@KH570 could obviously enhance the crystallinity of poly (L-lactic acid) (PLLA)/FA@KH570 composites, which accelerated the conversion from the liquid-liquid to the liquid-solid phase separation principle. Correspondingly, the controllable surface morphology from smooth to petal-like microspheres was attained simply by adjusting the FA@KH570 content. After coating nontoxic candle grease, the apparent contact angle of 5 wt% PLLA/FA@KH570 composite was significantly increased to an astonishing 151.2°, which endowed the composite with excellent anti-icing property. This strategy paves the way for recycling waste fly ash and manufacturing hydrophobic poly (L-lactic acid) composite for potential application as an anti-icing material for refrigerator interior walls.

Design of a Device and System to Study the Liquid–Solid-Phase Equilibrium Experiment of CO2 in PLNG

Pressurized liquefied natural gas (PLNG) is a new natural gas liquefaction solution proposed in recent years for reducing the construction and operating costs of floating liquefied natural gas (FLNG). For natural gas, the liquefaction temperature is strongly influenced by the pressure; when the pressure increases, the liquefaction temperature of natural gas increases accordingly. The increase in the liquefaction temperature of natural gas leads to a higher solubility of impurities such as carbon dioxide, which means that the pretreatment standards for liquefied natural gas can be reduced. Therefore, the use of PLNG technology can simplify pretreatment plants and significantly reduce construction and operating costs. In order to better apply PLNG technology to FLNG, it is necessary to understand the solubility of carbon dioxide in pressurized LNG and the phase change during liquefaction. To achieve this, experimental setups are needed to simulate the temperature and pressure environment of the LNG to obtain the relevant data and observe the relevant phenomena. After a literature research and analysis of the advantages and disadvantages of previous experimental setups, several improvements are proposed in this paper, and based on this, a visualization device is designed for studying the liquid–solid-phase equilibrium experiment of CO2 in PLNG. The device has a pressure resistance of 20 MPa, a minimum operating temperature of 77 K, and a variable volume function. It is also equipped with a sapphire window to be able to observe the inside of the device. In order to verify the superiority of the device, experiments were conducted using the device to verify the pressure resistance, variable volume, and visualization functions of the device. The experimental results show that the experimental device designed in this paper does have a certain superiority.

Zero-point motion of liquid and solid hydrogen

We present an inelastic neutron scattering study of liquid and solid hydrogen carried out using the wide Angular Range Chopper Spectrometer at Oak Ridge National Laboratory. From the observed dynamic structure factor, we obtained empirical estimates of the molecular mean-squared displacement and average translational kinetic energy. We find that the former quantity increases with temperature, indicating that a combination of thermal and quantum effects is important near the liquid-solid phase transition, contrary to previous measurements. We also find that the kinetic energy drops dramatically on melting of the crystals, a consequence of the large increase in molar volume together with the Heisenberg indeterminacy principle. Our results are compared with quantum Monte Carlo simulations based on different model potentials. In general, there is good agreement between our findings and theoretical predictions based on the Silvera-Goldman and Buck potentials.

Hydrate Reservoir Stimulation and Sand Control by Liquid-Solid Phase Change Proppant Filled in Radial Well

Summary The depressurization method for natural gas hydrate exploitation encounters the difficulties of low productivity and sand production. Enhancing hydrate production efficiency and reducing massive sand production are the key issues to be solved in hydrate development. This paper proposes a new approach to hydrate reservoir stimulation and sand control by liquid-solid phase change proppant (LSP) filled in radial well (SCRP). A multicomponent flow model of sand-water-gas-hydrate is established and applied to evaluate the effect of SCRP on hydrate development. The results obtained show that the application of SCRP realizes an integrative effect of both reservoir stimulation and sand control. Radial wells increase the sweep area of pressure drop and promote hydrate decomposition. Solid particles, which are formed by LSP, not only fill and support radial wells but also act as sand control medium, preventing sand from flowing into the production well. It is found that reducing the production pressure difference can effectively reduce sand production. To achieve a large-scale stimulated reservoir volume, it is necessary to increase the length of a single radial well, the number of radial wells in the same layer, and the number of radial well layers. The spiral layout of radial wells has a better effect on improving gas production. A single radial well achieves good sand control effect with the application of the LSP system, but an increase in radial well number leads to an increase in sand production, resulting in massive amounts of sand gathered in the production well. As a result, in the case of multiple radial wells, other sand control technologies, such as mechanical sand screening, should be used along with SCRP to further reduce sand production.

Evaluating the transferability of machine-learned force fields for material property modeling

Machine-learned force fields have generated significant interest in recent years as a tool for molecular dynamics (MD) simulations, with the aim of developing accurate and efficient models that can replace classical interatomic potentials. However, before these models can be confidently applied to materials simulations, they must be thoroughly tested and validated. The existing tests on the radial distribution function and mean-squared displacements are insufficient in assessing the transferability of these models. Here we present a more comprehensive set of benchmarking tests for evaluating the transferability of machine-learned force fields. We use a graph neural network (GNN)-based force field coupled with the OpenMM package to carry out MD simulations for Argon as a test case. Our tests include computational X-ray photon correlation spectroscopy (XPCS) signals, which capture the density fluctuation at various length scales in the liquid phase, as well as phonon density-of-states in the solid phase and the liquid-solid phase transition behavior. Our results show that the model can accurately capture the behavior of the solid phase only when the configurations from the solid phase are included in the training dataset. This underscores the importance of appropriately selecting the training data set when developing machine-learned force fields. The tests presented in this work provide a necessary foundation for the development and application of machine-learned force fields for materials simulations.

Quantitative Analysis of Transcription Termination via Position-Selective Labeling of RNA (PLOR) Method.

T7 RNA polymerase is the most widely used enzyme in RNA synthesis, and it is also used for RNA labeling in position-selective labeling of RNA (PLOR). PLOR is a liquid-solid hybrid phase method that has been developed to introduce labels to specific positions of RNA. Here, we applied PLOR as a single-round transcription method to quantify the terminated and read-through products in transcription for the first time. Various factors, including pausing strategies, Mg2+, ligand and the NTP concentration at the transcriptional termination of adenine riboswitch RNA have been characterized. This helps to understand transcription termination, which is one of the least understood processes in transcription. Additionally, our strategy can potentially be used to study the co-transcription behavior of general RNA, especially when continuous transcription is not desired.

Influence of ALS-linked M337V mutation on the conformational ensembles of TDP-43321-340 peptide monomer and dimer.

The transactive response (TAR) DNA/RNA-binding protein 43 (TDP-43) can self-assemble into both functional stress granules via liquid-liquid phase separation (LLPS) and pathogenic amyloid fibrillary aggregates that are closely linked to amyotrophic lateral sclerosis. Previous experimental studies reported that the low complexity domain (LCD) of TDP-43 plays an essential role in the LLPS and aggregation of the full-length protein, and it alone can also undergo LLPS to form liquid droplets mainly via intermolecular interactions in the 321-340 region. And the ALS-associated M337V mutation impairs LCD's LLPS and facilitates liquid-solid phase transition. However, the underlying atomistic mechanism is not well understood. Herein, as a first step to understand the M337V-caused LLPS disruption of TDP-43 LCD mediated by the 321-340 region and the fibrillization enhancement, we investigated the conformational properties of monomer/dimer of TDP-43321-340 peptide and its M337V mutant by performing extensive all-atom explicit-solvent replica exchange molecular dynamic simulations. Our simulations demonstrate that M337V mutation alters the residue regions with high helix/β-structure propensities and thus affects the conformational ensembles of both monomer and dimer. M337V mutation inhibits helix formation in the N-terminal Ala-rich region and the C-terminal mutation site region, while facilitating their long β-sheet formation, albeit with a minor impact on the average probability of both helix structure and β-structure. Further analysis of dimer system shows that M337V mutation disrupts inter-molecular helix-helix interactions and W334-W334 π-π stacking interactions which were reported to be important for the LLPS of TDP-43 LCD, whereas enhances the overall peptide residue-residue interactions and weakens peptide-water interactions, which is conducive to peptide fibrillization. This study provides mechanistic insights into the M337V-mutation-induced impairment of phase separation and facilitation of fibril formation of TDP-43 LCD.

Experimental Study on a Liquid-Solid Phase-Change Autogenous Proppant Fracturing Fluid System.

In this paper, a liquid-solid phase-change autogenous proppant fracturing fluid system (LSPCAP) was proposed to solve the problems that was caused by "sand-carrying" in conventional fracturing technology in oil and gas fields. The characteristic of the new fluid system is that no solid particles will be injected in the whole process of fracturing construction except liquids. The fluid itself will transform into solid particles under the formation temperature to resist the closure stress in the fractures. There are two kinds of liquids that make up the new fracturing fluid system. One of the liquids is called phase-change liquid (PCL) which occurs in the liquid-solid phase change under the formation temperature to form solid particles. Another is called nonphase-change liquid (NPCL) which controls the dispersity and size of PCL in the two-phase fluid system. Based on the molecular interaction theory and organic chemistry, bisphenol-A epoxy resin was selected as the building unit of the PCL, and the NPCL consisted of deionized water + nonionic surfactant. The test results indicated that the new fracturing fluid shows the properties of non-Newtonian fluid and has no wall-building property. The new fluid system has good compatibility with the formation fluid, conventional fracturing fluid, and hydrochloric acid. Through the filtration test, the filtration coefficients of PCL, NPCL, and mixture are found to be 1.56 × 10-4 m/s1/2, 2.66 × 10-4 m/s1/2, and 1.7 × 10-4 m/s1/2, respectively, and the damage rate of mixture and NPCL is 18 and 17.7%. The friction test results show that the resistance reduction rate reaches 69% when the volume ratio of PCL and NPCL is 1:10. The shear rate and time only affect the size of the autogenous solid particles, and the sorting coefficient (S) of the particles is 1.04-1.73, indicating good sorting. Crushing resistance and conductivity test results show that the crush rate of autogenous solid particles is 3.56-8.42%. The conductivity of the autogenous solid particles is better than those of quartz sand and ceramsite under a pressure of 10-30 MPa.

Feasibility study of AZ31B deposition made by novel powder bed friction stir process with optimal process parameters and tool features selection

The current work focused on the feasibility study of an in-house developed process at a laboratory scale named Powder Bed Friction Stir (PBFS) for AZ31B powder deposition. It employs friction stirring as a heating source instead of a laser or electron beam, as in powder bed fusion which can potentially mitigate the issues arising from liquid-solid phase transformation. A suitable process parameter and tool design was chosen through experimentation. Two sets of process parameters were selected for rotational and translational motion as 1200 rpm & 900 rpm and 360 mm/min & 200 mm/min, respectively. The material deposition is affected by tool design, so five different tools were explored. The overall height of the successful deposition was 7 mm with process parameters 1200 rpm & 360 mm/min, and (Circular Protruded Feature) CPFII tool in total 35 passes keeping layer thickness (0.2 mm). Microstructure and phase analysis were carried out using (Scanning Electron Microscopy) SEM and (X-ray Diffraction) XRD, respectively, to study the grain refinement, presence of (Inter Metallic Compounds) IMCs, and participation of the slip system in the deformation process. The resulting grain refinement was 78%, with increased basal plane intensity in the deposit. The current study offered an extension of solid-state additive manufacturing as PBFS for Mg alloys.

Graphitizing modification of the axial zone of cast iron rolling rolls in the liquidus-solidus temperature range

Purpose. To develop a method for calculating a process of graphitizing modification of unsolidificated liquid-solid zone to reduce transcrystallinity of the macrostructure and the amount of cementite in the center of castings. Methodology. The duration of solidification of the castings was determined by the kinetic curves of liquidus, solidus and pouring boundary in coordinates of relative thickness of the solidified metal layer – the parametric criterion of Gulyaev. Findings. A methodology for the process of modification of the axial zone of rolling was developed, the mass and time of adding aluminum were determined according to the amount of liquid-solid phase that remains after the solidification of the working layer. On the example of a rolling roll weighing 1115 kg, 0.488 kg of aluminum was added into liquid-solid zone after the working layer solidified. Movement of aluminum to the front of crystallization is provided by centrifugal forces and adding of aluminum along the height of the roll. Originality. For the first time, the kinetic curves of liquidus, solidus and pouring boundary have been plotted in coordinates of the relative thickness of the solidified metal layer x/R and /R2 – the parametric criterion of Gulyaev for rolled cast iron alloys cooled in chill-sand molds of various sizes. A methodology was developed for calculating the process of aluminum modification of the axial zone of rolling rolls after solidification of the working layer in the barrel which was set at the pouring boundary. The amount of aluminum depends on the remains of the liquid-solid phase. Practical value. Graphitizing modification reduces transcrystallinity of the macrostructure and the amount of cementite in the axial zone of castings. A promising direction for further development is the development of new methods for manufacturing castings due to physical and mechanical effects on the two-phase zone, deoxidation and alloying of the central zones of castings.