Search

The present study focuses on investigating the microstructure, hardness, wear, and corrosion resistance of Al1.2CoCrFeNiScx high entropy alloys, where the Sc content (x) varies between 0, 0.1, 0.2, and 0.3. The results indicate that the addition of Sc promotes the formation of the FCC phase and improves the hardness and wear resistance, but reduces the corrosion resistance of the alloy. The alloy's evolution can be observed as a transition from a single BCC phase to a combination of Fe, Cr-rich BCC phase, Al, Co, Ni-rich BCC phase, and Ni, Sc-rich FCC phase. As the Sc content increases from 0 to 0.3, the hardness increases from 438 HV to 581 HV, representing a 32.6 % increment. This increase can be mainly attributed to grain size strengthening and solid solution strengthening. Additionally, the average friction coefficient experiences a notable reduction from 0.999 to 0.574, indicating a 42.5 % decrease. With respect to wear resistance, the Al1.2CoCrFeNiSc0.3 alloy exhibits superior performance, demonstrated by its lower friction coefficient, reduced wear rate, and smaller volume, width and depth of wear marks. Furthermore, the addition of Sc to the Al1.2CoCrFeNiScx alloys leads to an overall decrease in corrosion potential, accompanied by an increase in corrosion current density, suggesting that Sc has a detrimental effect on the corrosion resistance of the alloy. Moreover, the Al1.2CoCrFeNi alloy displays pitting corrosion, while the Al1.2CoCrFeNiScx alloys demonstrate intercrystalline corrosion, which preferentially occurs on the Ni, Sc-rich phase due to the high electrochemical activity and low equivalent chemical potential.

An inhibitor that can effectively inhibit shale hydration is necessary for the safe and efficient development of shale gas. In this study, a novel ionic liquid copolymer shale inhibitor (PIL) was prepared by polymerizing the ionic liquid monomers 1-vinyl-3-aminopropylimidazolium bromide, acrylamide, and methacryloyloxyethyl trimethyl ammonium chloride. The chemical structure was characterized using fourier transform infrared spectroscopy (FT-IR) and hydrogen-nuclear magnetic resonance (H-NMR), and the inhibition performance was evaluated using the inhibition of slurrying test, bentonite flocculation test, linear expansion test, and rolling recovery test. The experimental results showed that bentonite had a linear expansion of 27.9% in 1 wt% PIL solution, 18% lower than that in the polyether amine inhibitor. The recovery rate of shale in 1 wt% PIL was 87.4%. The ionic liquid copolymer could work synergistically with the filtrate reducer, reducing filtration loss to 7.2 mL with the addition of 1%. Mechanism analysis showed that PIL adsorbed negatively charged clay particles through cationic groups, which reduced the electrostatic repulsion between particles. Thus, the stability of the bentonite gel systems was destroyed, and the hydration dispersion and expansion of bentonite were inhibited. PIL formed a hydrophobic film on the surface of clay and prevented water from entering into the interlayer of clay. In addition, PIL lowered the surface tension of water, which prevented the water from intruding into the rock under the action of capillary force. These are also the reasons for the superior suppression performance of PIL.

Magnons in antiferromagnets hold potential for chirality-based spintronics, but a practical platform remains absent. Here, the authors demonstrate possible magnon chirality switching, reading and modulation in an artificial ferrimagnet Py/Gd/Py/Gd/Py/Pt multilayer, manifesting the chirality as an independent degree of freedom.

Ensuring wellbore stability is of utmost importance for safety when drilling in deep formations. However, high temperatures severely disrupt the drilling fluid gel system, leading to severe stability issues within ultra-deep formations containing micropores. This study focused on the development of a polymer-based plugging material capable of withstanding high temperatures up to 200 °C. A kind of microsphere, referred to as SST (styrene–sodium styrene sulfonate copolymer), was synthesized with a particle size of 322 nm. Compared to polystyrene, the thermal stability of SST is greatly improved, with a thermal decomposition temperature of 362 °C. Even after subjecting SST to hot rolling at 200 °C for 16 h, the particle size, elemental composition, and zeta potential remained stable within an aqueous dispersion system. The results of core displacement and NMR tests demonstrate that SST considerably reduces the pore diameter with a remarkable plugging efficiency of 78.9%. Additionally, when drilling fluids reach 200 °C, SST still enhances drilling fluid suspension and dispersion, and reduces fluid loss by over 36% by facilitating the dispersion of clay particles, improving the gel structure of the drilling fluid, resisting clay dehydration, and promoting plugging. The development of SST provides valuable insights into the preparation of high-temperature-resistant microspheres and the formulation of effective plugging agents for deep-well drilling fluids.

With the gradual depletion of shallow oil and gas, deep oil and gas has become the focus of development. However, deep formations generally face the challenge of high-temperature and high-salinity, and drilling fluid agents are prone to failure, leading to drilling fluid intrusion into the formation that can cause serious drilling accidents such as well bore collapse. For this, a styrene-based nano-microsphere (SSD) modified with amphoteric ions was developed, with a particle size of 228 nm which could resist temperatures up to 200 °C and sodium chloride (NaCl) up to saturation. SSD has significant salt-responsive properties and its aqueous dispersion becomes transparent with increasing salinity. The SSD provided superior plugging performance in solutions containing NaCl, with a core plugging efficiency of 95.2%, and it was significantly better than the anion-modified microspheres. In addition, in drilling fluids under high temperature and high-salinity conditions, the SSD promotes particle gradation of drilling fluids and improves the zeta potential through its own plugging and synergistic effect with clay, which significantly improves the comprehensive performance of drilling fluids, such as stability, rheological performance, and filtration reduction performance. The development of SSD provides a new idea for research of high-temperature and high-salinity-resistant drilling fluid agents.

Large strain gradient is crucial for flexoelectricity. Here, the authors reveal the generality and tunability of large strain gradients at grain boundaries in oxides, explaining the possible effects on the electrical activities of ceramics.

Long-distance magnon transport is highly desired for magnonics. Here, the authors demonstrate a millimetre-long magnon decay length in multiferroic heterostructures, which is attributed to magnon-polarons induced by the magnetoelastic coupling.

A controllable magnetoelectric phase based on symmetry engineering is challenge in natural bulk crystals. Here, via engineering of interfacial Dzyaloshinskii-Moriya interaction, the authors design a magnetoelectric phase transition in oxide superlattices of correlated electron systems.

The majority of polar structures emerging naturally in ferroelectrics are topologically trivial. Here, the authors demonstrate reconstruction of topologically trivial strip-like domain architecture into arrays of polar vortex in (PbTiO3)10/(SrTiO3)10 superlattice.

The effects of critical defects on stress corrosion cracking (SCC) of Al–7.82Zn–1.99Mg–2.41Cu–0.12Zr alloy under under-ageing (UA), peak-ageing (PA) double-ageing (DA) and retrogression and reageing (RRA) were investigated. It is found that anodic dissolution of grain boundary precipitates (GBPs) for UA sample generates critical defects due to low Cu content of GBPs, whereas the dissolution of Al, Mg and Zn elements within the grain interior is responsible for the formation of critical defects for PA, DA and RRA samples. The high distribution continuity of GBPs promotes the continuous propagation of stress corrosion crack along grain boundary, leading to intergranular SCC for UA sample. Coarsened GBPs which are distributed discontinuously could hinder anodic dissolution along the grain boundary. As a result, the cracks propagate along the grain interior, causing transgranular SCC for DA sample. And large size and low density of matrix precipitates (MPTs) decease SCC susceptibility. Al7Cu2Fe particles promote the dissolution of the surrounding matrix, inducing local stress concentration, and thus leading to the generation of stress corrosion cracks.

Band-filling control of transition metal ions in oxide heterostructures is typically limited to the two-dimensional interface. Here, the authors report a three-dimensional modulation of the band-filling and a topotactic phase transition in LaCoO3, triggered by charge transfer at LaCoO3/LaTiO3 interface.

While the role of PbTiO3 in PbTiO3/SrTiO3 superlattices has been widely studied, little attention is paid to possible polar topologies in SrTiO3. Here, the authors create atomic-scale vortex–antivortex pairs in the superlattices, expanding the understanding of topological structures.

Controlling topological polar vortices promises to open up new applications for ferroelectric materials. Here, the authors proposed a method to mechanically manipulate polar vortices and monitored the transition between vortex and ferroelectric phase by in-situ scanning transmission electron microscopy.

In order to prevent collision of complex structure well, accurate measurement of the distance of adjacent wells must be required during the development of the unconventional reservoir. The precision of the traditional survey tools and scanning software is not accurate enough. Based on the electromagnetic anticollision measuring calculation method, the electromagnetic anticollision detection tool was designed and simulation experiments were carried out. The influence of different position relations between sensor and casing on magnetic field strength detected by the sensor was analyzed. When the sensor and the casing were parallel and the distance of them was 0.5 m∼3 m, the tool could calculate accurately the distance and orientation of the adjoining well. When the angle between the sensor and the casing was within 50°, the calculation result was accurate. This research result validated the accuracy of the principle of the electromagnetic anticollision tool while drilling cluster well, and it could provide theoretical support for the development of electromagnetic detection tools.

In tunnel design and construction, proper and accurate classification of rock surrounding tunnels is needed to ensure tunnel construction safety, guarantee construction quality, and reduce project costs. With rapid urbanization, numerous small clear-distance tunnels have been constructed in dense urban road networks. Compared with ordinarily separated tunnels, the construction scale and difficulty of small clear-distance tunnels are greater, and the requirements for the classification of rock surrounding tunnels are accordingly higher. A small clear-distance tunnel in an urban super large and complex underground interchange hub of the Xiamen Haicang Evacuation Channel was selected as the background, and the classification method of the middle rock pillar in a small clear-distance tunnel is presented based on the general classification standard of surrounding rocks. Based on the geometric, physical, and mechanical factors of the middle rock pillar, six indices affecting the stability and quality of the middle rock pillar were selected, and the classification index system of the middle rock pillar was established from the two dimensions of the basic and auxiliary indices. The basic and auxiliary indices were scored using the scoring method, and the different grades of the middle rock pillar were divided according to different scores. The middle rock pillar classification standard was applied to the quality assessment of the middle rock pillar, which provided a basis for the on-site assessment of the quality of the middle rock pillar and proved the accuracy and superiority of the improved classification standard. The newly established classification standard can provide a reference for selecting the correct construction method and supporting structure type for small clear-distance tunnels.

Ridge slopes often occur in highway or railway engineering. The initial stress distribution of a ridge slope is important for the original slope and an excavation slope. In this paper, a wire-frame model of ridge slope was established. Numerical simulations on the 3D stability analysis were performed using the strength reduction method based on unified strength theory. The influences of ridgeline dip angle α, flank slope angle β, and slope height H on the deformation and failure mode of ridgeline slopes were analyzed. When α was small, cracking failure easily occurred at the front edge of the ridge slope and the area near the ridge line. When α was large, shear failure was prone to occur at the trailing edge of the ridge slope. Under the same reduction coefficient, the larger the flank slope angle β, the larger the slope displacement of the ridge. The plastic zone gradually concentrated near the ridge. When H was small, the displacement mainly occurred at the trailing edge of the slope, and the slopes were generally prone to cracking damage at the trailing edge. The front edge of the slope experienced a large displacement when the height of the ridge slope increased. The bottom of the flank slope was also displaced, and a plastic zone was observed at the foot of the slope. When the excavation slope ratio of the ridge slope was small, the plastic zone was mainly located on the side slope. When the excavation rate increased, the plastic zone appeared on the excavation slope surface, and its stability decreased significantly.

During underground space exploitation in the urbanization process, numerous foundation pits were constructed where a diaphragm wall was often used as a retaining structure and waterproof curtain. Due to complicated engineering geological conditions or improper construction, diaphragm walls and wall joints often exhibit quality defects. Groundwater leaked from these quality defects to foundation pits during excavation, endangering the safety of the pit and surrounding facilities. The current leakage identification of the underground retaining structure was performed by artificial visual detection, which cannot satisfy the engineering requirement. The temperature field in the leakage area of the diaphragm wall was different from other areas. The leakage wall imaging system using a thermal imager was efficient in visualizing leaking, which was not visible to the naked eye. In this study, infrared thermal imaging technology was introduced in potential leakage detection for the diaphragm wall of a foundation pit. The infrared radiation characteristics of the diaphragm wall leakage and the potential leakage parts were studied through laboratory simulation tests and on-site detection methods. The maximum temperature appeared at the water outlet and the surface of the defect with hidden defect, and the temperature field was symmetrically distributed along the cross-section direction. In the potential leakage area, the temperature difference at the penetration point was 23.4 °C when the initial water pressure was 10 kPa. The temperature difference at the penetration point was 21.8 °C when the initial water pressure was 30 kPa. In the field test, the maximum temperature difference between the leakage area and the surrounding wall was 4.5 °C. The study can provide a reference for similar engineering.

Leakage in the diaphragm wall is difficult to detect in deep foundation pits. In this study, the conceptual model of active and passive thermal leak detection methods was proposed according to the occurrence of temperature field anomalies caused by seepage. Experiments were performed using a heating system and an optical fiber temperature measurement system to verify the thermal leakage detection systems. Numerical simulations were performed to understand the mechanism of the detecting method. Results indicated that the optical cable could detect the low-temperature anomaly in the active temperature field leak detection. The arrangement method of the leakage detection system was also presented in actual engineering.

Abstract Wellbore instability happens mostly in the shale formation. Early researches have studied thoroughly on the physicochemical and mechanical mechanism that causes instability. However, only a few works have considered the influence of field drilling operations, such as drill pipe rotation. In this paper, a true triaxial cell is used to simulate the downhole field situations, and a drill pipe rotation device is innovatively designed and implemented into the true triaxial cell. Using this facility, the influence of drill pipe rotation on shale instability has been performed. Different rotation speed, weight on bit, drilling fluid pressure, and microcracks on borehole have been considered. The enlargement of the wellbore is quantitatively plotted and compared. Results show that the drill pipe rotation contributes to a more enlargement of the wellbore, and a higher rotation speed causes a more severe collapse. The drill string weight on bit also contributes to the enlargement of the wellbore, with a larger weight on bit induces a larger diameter of the collapsed wellbore. Compared with the rotation speed and weight on bit, the influence of drilling fluid density is relatively less significant. However, the influence of microcracks caused by hitting of drilling tools is profound. For a cracked shale formation, the wellbore diameter can be enlarged for more than 40%. Then, the variation of borehole collapse with time and depth under drill pipe rotation influence is analyzed. In all of these four factors, the significant sequence is microcracks > weight on bit > rotation speed > drilling fluid pressure. In all the collapse phenomena, the collapse is more severe in the minimum horizontal stress direction. This is explained by the analysis of the stress distribution in the whole circumferential angle (360°) of the wellbore. Overall, this work fills the gap of the influence of drilling operations on wellbore instability.

Close excavation section spacing, the mutual influence and interpenetration of various processes, and the multiple disturbances of the middle rock pillar in a small clear-distance tunnel pose great difficulty to construction. This study adopted the small clear-distance tunnel of Xiamen Haicang Evacuate Channel as the research object. The tunnel belonged to a small clear-distance tunnel in an urban super large and complex underground interchange hub where complex adjacent small clear-distance tunnels were adopted. ABAQUS was used to analyze the influence of different excavation schemes, lithological grades, and footage lengths for tunnel stability. The deformation and stress characteristics of the tunnel’s surrounding rock and lining structure in different excavation schemes (full section method, bench method, center diaphragm (CD) method, and double wall heading method), lithological grades (III, IV and V), and footage lengths (3 m, 4 m and 5 m) were introduced. The results showed that the double wall heading method could effectively control the horizontal displacement of the hance, and the overall stress state of the lining in the CD and double wall heading methods were reasonable. The vertical displacement of the surface and vault was positively correlated with the elastic modulus of the rock mass. When no temporary support was present in the grade V rock mass, the area from the hance to the arch foot was prone to large deformation. Reducing the footage was beneficial to controlling the deformation of the vault and hance. This study can provide a reference for the on-site construction of small clear-distance tunnels.

Large section tunnels have huge excavation spans, complex excavation procedures, mutual influence among various procedures, multiple disturbances of the surrounding rock, and discontinuous connection among linings under different procedures, which bring great difficulties to their construction. The Caijianwei Mountain No. 2 tunnel of the Xiamen Haicang Evacuate-channel project in China belongs to a super large section tunnel. The tunnel’s maximum excavation section span reaches 30.52 m, and the excavation area reaches 421.73 m2. Its excavation sequence, the timing of the second primary lining support, temporary support disassembly, and secondary lining support of the double-side heading method were analyzed using numerical methods. The excavation sequence of the double side-heading method from the right pilot tunnel to the left pilot tunnel and then to the middle pilot tunnel can avoid a large horizontal displacement at the arch waist and control the deformation of the lining. The excavation sequence from the middle pilot tunnel to the two side pilot tunnels was conducive to the bearing performance of the concrete at the arch crown. The excavation sequence from the two side pilot tunnels to the middle pilot tunnel can better protect the concrete safety at the arch waist. The timing of the second primary lining support, temporary support removal, and secondary lining support have different effects on the deformation and stress of the surrounding rock and support structures. In the construction process, the timing of the second primary lining support, temporary support disassembly, and secondary lining support should be determined according to the actual deformation and stress of the site section. The research results can provide a reference for the construction design of the double-side heading method for large section tunnels.

Understanding the atomic arrangement and binding nature of 2D materials with substrates is crucial to understand their properties and utilize their functions. Here, authors report that at high temperature graphene and α-Al2O3 substrate form a C-O-Al bond, having strong interactions, while interfacial structural relaxations of sapphire remain suppressed.

Summary: Oxide-based resistive switching devices, including ferroelectric tunnel junctions and resistance random access memory, are promising candidates for the next-generation non-volatile memory technology. In this work, we propose a ferroionic tunnel junction to realize a giant electroresistance. It functions as a ferroelectric tunnel junction at low resistance state and as a Schottky junction at high resistance state, due to interface engineering through the field-induced migration of oxygen vacancies. An extremely large electroresistance with ON/OFF ratios of 5.1×107 at room temperature and 2.1×109 at 10 K is achieved, using an ultrathin BaTiO3-δ layer as the ferroelectric barrier and a semiconducting Nb-doped SrTiO3 substrate as the bottom electrode. The results point toward an appealing way for the design of high-performance resistive switching devices based on ultrathin oxide heterostructures by ionic controlled interface engineering. : Interface Science; Transport Property of Condensed Matter; Devices Subject Areas: Interface Science, Transport Property of Condensed Matter, Devices

The excavation of a shallow buried tunnel may cause stress redistribution in surrounding rock, and cause deformation, damage, and even destruction of adjacent underground pipelines. The land part of the Haicang undersea tunnel in Xiamen of China was a super shallow buried large span double-arch tunnel. Its construction was restricted by both underground excavation safe and adjacent pipeline protection. Multiple groups of working conditions were designed considering the relative position of pipe and tunnel, pipeline and tunnel construction parameters. Numerical simulation was used to study the influence of pipeline horizontal distance, buried depth, pipeline diameter, pipeline wall thickness, pipeline shape, pipeline material and excavation method on the response of adjacent underground pipelines. The results show that the relative position of pipe and tunnel, and the construction method of the double-arch tunnel have a great influence on pipeline deformation. Pipeline material, pipeline diameter and excavation method have a great influence on pipeline stress. The construction method was the key factor affecting the stress and deformation of the pipeline. The three-step reserved core soil method can effectively control the stress and deformation of underground pipelines. The research results can provide a reference for similar projects.

Ultra-shallow-buried and large-span double-arch tunnels face complex risks during construction. The risk sources are hidden, complicated, and diverse. The dynamic risk assessment problem cannot be solved satisfactorily by using the static method as an insufficient amount of research has been conducted. The land part of the Xiamen Haicang double-arch tunnel was selected as the background for the dynamic risk assessment of ultra-shallow-buried and large-span double-arch tunnel construction. The construction process was divided into five stages: pre-construction preparation; ground and surrounding rock reinforcement; pilot tunnel excavation; and the single-and the double-tunnel excavations of the main tunnel. Through consultation with tunnel experts, six first-level and thirty second-level risk evaluation indexes were proposed. The benchmark weight of the dynamic risk assessment index was determined by using the analytic hierarchy process. The weight of the risk evaluation index was revised according to the monitoring data and the construction stage. The fuzzy evaluation matrix of the construction risk membership degree was obtained by using the fuzzy comprehensive assessment method, and the calculation results were analyzed using the subsection assignment method. Control measures were suggested according to the risk assessment results. The risk assessment result of the double tunnel excavation stage of the main tunnel was level II, and the risk level was the highest among the five construction stages. The risk assessment result of the ground and surrounding rock reinforcement stage was level IV, and the risk level was the lowest. The dynamic construction safety risk assessment based on the fuzzy comprehensive assessment method is more timely, accurate, and reasonable than the traditional assessment method. The method can be adopted in similar engineering projects.

The temporal and spatial effects of a complicated excavation process are vital for an ultra-shallow buried large-span double-arch tunnel excavated under an expressway in service. Numerical simulations are urgent and necessary to understand the effect of the total construction process. Taking Xiamen Haicang tunnel as a research object, the total excavation process of three pilot tunnels and the three-bench reserved core soil method of an ultra-shallow buried large-span double-arch tunnel with a fault fracture zone under an expressway was simulated using software FLAC3D. The deformation of the surface, surrounding rock, underground pipelines, tunnel support structure and partition wall of the three pilot tunnels and the main tunnel was analyzed, and the dangerous areas and time nodes were obtained. When the tunnel was excavated to the fault fracture zone, the deformation of the surface and surrounding rock increased significantly. The rock and soil within 20 m behind the excavation surface of the pilot tunnel were greatly disturbed by the excavation. During the excavation of the main tunnel, the horizontal displacement of the middle partition wall moved slightly towards the main tunnel excavated first. The research results can provide a reference for the construction design of double-arch tunnels.

For an ultra-shallow buried double-arch tunnel with a large cross-section, the arching effect is difficult to form in surrounding rock, and grouting method is often adopted to reinforce the surrounding rock. Hence, examining the grouting reinforcement parameters is of great significance for potential failure and collapse prevention. The land part of Haicang undersea tunnel was selected as a case study; laboratory experiments, theoretical analysis, and numerical simulation were performed to determine the grouting solid strength and grouting reinforcement parameters. The effects of different water–cement ratios on slurry fluidity, setting time, bleeding rate, and sample strength were studied by laboratory experiments. A method was proposed to determine the shear strength parameters of grouted surrounding rock through the grout water–cement ratio and the unconfined compressive strength of the rock mass. Numerical simulations were performed for grouting reinforcement layer thickness and the water–cement ratios. The deformation and stability law of tunnel surrounding rock and its influence on surrounding underground pipelines were obtained considering the spatial effect of tunnel excavation and grouting reinforcement. The reasonable selection range of grouting reinforcement parameters was proposed. The initial setting time and bleeding rate of cement slurry increased with the increasing water–cement ratio, while the viscosity of cement slurry and sample strength decreased with the increasing water–cement ratio. The shear strength parameters of grouted surrounding rock were determined by the water–cement ratio of grout and unconfined compressive strength of rock mass before grouting. When the thickness of grouting reinforcement layer h = 1.5 m and the water–cement ratio of grout was suggested η = 0.85, the surface settlement, the deformation of the vault, and the deformation of the nearby pipeline all met the design. Moreover, the construction requirements were more economical. Research results can provide a reference for the selection of grouting reinforcement parameters for similar projects.

Taking the Zigaojian tunnel, Hangzhou–Huangshan high-speed railway, China, as background, the rock mass structure effect on smooth blasting quality was studied. Four rock mass structures were determined on the basis of the information collected on the tunnel site. Smooth blasting finite element models were established using LS-DYNA. The accuracy of the numerical calculation model was verified by comparing the overbreak and underbreak between the numerical simulation and monitoring. Orthogonal numerical test was used to study the rock mass structure effect through single factor and main effect analysis methods. With the decrease in rock mass integrity, the smooth blasting overbreak of tunnels with massive integrity structure, massive structure, layered structure, and cataclastic structure increased. For massive integrity structure and cataclastic structure, the peripheral hole spacing should be emphatically considered. Meanwhile, in massive structure and layered structure, the included angle and spacing of structural planes had a great influence on the smooth blasting quality. The research results could provide a reference to improve the quality of similar tunnel smooth blasting.

Graphene is a single atom thick crystal composed of carbon atoms. It is the lightest, thinnest, strongest material that conducts heat and electricity well heretofore. In terms of application, by introducing oxygen-containing groups, graphene can be well dispersed in solvents, can be chemically modified and functionalized, or connected with other electroactive substances through covalent bond or non-covalent bond to form composite materials, which is conducive to further processing and promotion. The application of graphene in oilfield chemistry started late, but developed rapidly. Graphene has played an active role in drilling fluid, cementing fluid, fracturing fluid, displacement fluid and other oilfield working fluids. It can enhance the temperature and salt resistance of working fluid and improve the effect of working fluid. In this paper, several directions of graphene applications in oilfield chemistry, such as modified graphene, graphene copolymers and graphene nanoparticles, are reviewed in detail from the synthesis methods, action mechanisms and effects of graphene and its derivatives, and the frontier cases at this stage are given. On the basis of the existing research, suggestions for the development direction of graphene materials in oilfield chemistry are given for a variety of graphene materials, aiming to provide guidance for the application of graphene in oilfield chemistry. [ABSTRACT FROM AUTHOR]

Misfit dislocations at a heteroepitaxial interface produce huge strain and, thus, have a significant impact on the properties of the interface. Here, we use scanning transmission electron microscopy to demonstrate a quantitative unit-cell-by-unit-cell mapping of the lattice parameters and octahedral rotations around misfit dislocations at the BiFeO3/SrRuO3 interface. We find that huge strain field is achieved near dislocations, i.e., above 5% within the first three unit cells of the core, which is typically larger than that achieved from the regular epitaxy thin-film approach, thus significantly altering the magnitude and direction of the local ferroelectric dipole in BiFeO3 and magnetic moments in SrRuO3 near the interface. The strain field and, thus, the structural distortion can be further tuned by the dislocation type. Our atomic-scale study helps us to understand the effects of dislocations in this ferroelectricity/ferromagnetism heterostructure. Such defect engineering allows us to tune the local ferroelectric and ferromagnetic order parameters and the interface electromagnetic coupling, providing new opportunities to design nanosized electronic and spintronic devices. [ABSTRACT FROM AUTHOR]