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To overcome the limitation in formability at room temperature, manufacturers have developed magnesium alloys with remarkable properties by adding rare-earth elements. The rare-earth magnesium alloys behave differently from the conventional alloys, especially with respect to their coupled anisotropic and strain rate sensitive behavior. In the current work, such behavior of the rare-earth Mg alloy ZEK100 sheet at room temperature is investigated with the aid of the elastic viscoplastic self-consistent polycrystal plasticity model. Different strain rate sensitivities (SRSs) for various deformation modes are employed by the model to simulate the strain rate sensitive behaviors under different loading directions and loading rates. Good agreement between the experiments and simulations reveals the importance and necessity of using different SRSs for each deformation mode in hexagonal close-packed metals. Furthermore, the relative activities of each deformation mode and the texture evolution during different loadings are discussed. The anisotropic and strain rate sensitive behavior is ascribed to the various operating deformation modes with different SRSs during loading along different directions.

The 3D visualization of the porosity in high-pressure die casting (HPDC) Mg alloys AZ91D and Mg4Ce2Al0.5Mn (EA42) was investigated by X-ray computed tomography. It was demonstrated that the volumetric porosity at the near-gate location for alloy EA42 was significantly higher than that far from the gate location. This difference resulted from the low valid time during intensified casting pressure conditions. Specimens of alloy EA42 exhibited a narrow pore distribution in the side view (∼0.5 mm) compared to the wide distribution (∼1.8 mm) of alloy AZ91D, which was mainly attributed to the formation mechanism of the defect band. The formation of microporosity in the defect band of alloy EA42 was inhibited because of the significant latent heat released by a large amount of the Al11Ce3 phase segregated in the defect band during solidification. Additionally, an effective estimator (Z-Propagation) was introduced, which is proposed to predict the projected area fraction of the porosity (f) involved during tensile failure with better effectiveness compared with traditional methods based on the actual fractured surface. By coupling the Z-Propagation method with the critical local strain model, the logarithmic fracture strain and true fracture stress of the specimens were predicted within 3.03% and 1.65% of the absolute value of the average relative error (AARE), respectively.

In this study, the microstructure, thermal conductivity, and mechanical properties of Mg–4La–xAl–0.5Mn (x = 0, 0.5, 1, 1.5, 2, and 2.5 wt%) alloys were investigated. As the Al content of the alloys increases, the continuous network Mg12La phase is gradually replaced by non-network Al–La phases. The types of Al–La phases depend on the Al content. When the Al content is relatively low, the alloy tends to form Al2La or Al53La22 phases; otherwise, it tends to form an Al11La3 phase. The concentration of the Al solute atoms in the α-Mg matrix increases gradually as the Al content increases. The thermal conductivity is very sensitive to the concentration of Al solute atoms. The thermal conductivity of high-pressure die cast Mg–4La–2.5Al–0.5Mn alloy is 106.5 W/(m·k) and its yield stress, tensile strength, and elongation are 149 MPa, 253 MPa, and 11.5%, respectively.

Twin Marine Lifter (TML) is a specially designed heavy-lifting system consisting of two vessels for offshore installation & decommissioning. The system is developed multi-functionally in the heavy lifting sector to be cost-effective. Conceptually, they can be used in tandem for the platform installation and decommissioning of both topsides and jackets or carrying out by single lift configuration for other offshore construction tasks such as wind farm equipment installation. These flexible and versatile solutions to a wider range of potential clients also constrain the shape and the main particulars of the vessels, which results in extra challenges coming from the stability properties of the specific multi-body system compared to traditional single vessel operations, and there are few literatures could be referred to. In view of the highly complicated motions in the multi-body system at lifting phases, the topological model reflecting the flexible connections among bodies in system during the operation is constructed to obtain theoretical estimation of the roll stability of the targeted decommission topside. The virtual prototype technology based on ADAMS (Automatic Dynamic Analysis of Mechanical Systems) considering the coupling boundary of control factors including capability of the DP power and the compensation system are introduced by experimental data to correctly estimate the influence of multi-body motions on the roll stability of the topside in a synchronized way. A fast analysis and prediction methodology on the roll stability limiting criteria of the multi-body system is proposed. It would provide a safety guarantee and technical support for the design of the specific apparatus and the successful decision making on schemes of a new type of offshore operation mode.

TLS (Topsides Lifting System) utilization is a modern fast lifting technology developed for offshore platform installation. The positive prospects have seen from its sound and efficient performance at the offshore operation. To improve the feasibility of dual barge float-over operations, two new individual barges are designed in application with TLS. The targeting TLS system is equipped with motion compensation system that consists of several sets of lifting beams. Because the flexible mechanical couplings and the hydrodynamic interactions between bodies, the dynamic characteristics of system will be more complex. Some of the eigen modes might be excited by wave loads and could potentially lead to large responses. To demonstrate the dynamic properties of the new operation mode, a mechanical and hydrodynamic coupled multi-body model is established. Each lifting beam is modeled as a rigid body with X and Y degree of freedom relative to the barge. The motion compensation system is considered with a passive mode, and a spring-damper model is used to simulate its property. The coupled hydrodynamic forces of two barges are analyzed first. The eigen value analysis is conducted to identify the natural periods and eigen modes of the coupled multi-body system. A strong coupling of roll and sway motions of barge, and the heave motion of topside is observed. The sensitivity study about the parameters of lifting beams for system natural periods are carried out. The motions of barges and topside and the global dynamic loads acting on topside in regular waves are also presented. The results indicate that the heave motions decrease but the roll and pitch motions increase at their natural frequency compared with motions of the rigid connected system. The global dynamic loads acting on topside are decreased. The analyzed dynamic properties provide an initial cognition reference of the new operation system and help with the system design especially for TLS.

The hot tearing behavior of the double ternary eutectic alloy system, Al-6Mg-xSi (0 to 6.0 wt pct Si) alloys, was evaluated by a constrained rod casting mold equipped with a thermocouple and a load cell connected to a data acquisition system. Experimental results were compared with the results calculated by Scheil’s model using Pandat software to predict the occurrence of hot tearing in Al-6Mg-xSi alloys. The curve of hot tearing susceptibility contained two peaks, which were mainly affected by the double ternary eutectic reactions and the solidification phases evolution. And it agreed with the Kou’s hot tearing index precisely. The types and fractions of solidification phases (Al3Mg2, Mg2Si, and eutectic Si) determined by the addition of Si content changed the freezing range and eutectic liquid fraction greatly. In addition, the types, fractions, sizes, and distributions of solidification phases affected the nucleation, propagation, and healing of hot tear cracks. The maximum contraction force value decreased as the reduction of volume shrinkage coefficient due to the addition of Si content. The drop-in force value on the contraction force curve could indicate the occurrence of hot tearing, and predict the hot tearing susceptibility when considering the shrinkage coefficient.

Few studies were reported on the phases’ relationships of AE44 (Mg-4.0Al-4.1RE-0.3Mn, wt.%) and its composites. In this work, AE44 alloy and Saffil (δ-Al2O3)/AE44 Metal matrix composite (MMC) were both prepared by slow shot high pressure die casting (SS-HPDC) technology and their phase constitutions were all studied in detail using experimental techniques combined with CALPHAD (Calculation of Phase Diagram) modeling. The results revealed that the alloy consists of the α-Mg matrix, Al11RE3 intermetallic phase, and one trace phase Al3RE, while the composite contains five major phases: α-Mg, δ-Al2O3, Al3RE, MgO and Mg2Si, and two trace phases of Al2RE and Al11RE3, respectively. Al11RE3 is partly derived from Al2RE, while Al3RE is a product of the peritectoid reaction between the two precipitates. The presence of MgO and Mg2Si is due to the interfacial reaction between the SiO2 binder in the fiber preforms and the molten magnesium during infiltration. The use of SiO2 binder in the preform manufacturing was limited/minimized to reduce the MgO formation in the MMC casting process, which can be detrimental to the fatigue performance of the MMC materials.

The oxidation mechanism for the molten surface of Al–5Mg–2Si–Mn alloy was studied. The results show that the oxide layer contains MgO, Al2O3, MgAl2O4, BeO and SiO2, and it is composed of a composite inner layer (MgO/Al2O3/MgAl2O4/BeO/SiO2) and an outer layer of MgO. An oxidation mechanism was proposed to describe the four oxidation stages which included oxidation adsorption, accelerated oxidation, transitional oxidation and stable oxidation. The effects of oxidation time and oxidation temperature on the thickness of oxide layer were discussed. Thermodynamic calculations were used to confirm the feasibility of oxidation process, indicating that MgO was the most stable oxide in the experimental temperature range. Further, the stable regions of MgO and MgAl2O4 as functions of magnesium content and oxidation temperature were calculated. In the stable oxidation stage, the diffusion activation energy of Mg atoms in MgO was fitted according to the outer layer thicknesses, and the kinetic equation of the outer layer thickness with the oxidation time and oxidation temperature was established. From the perspective of thermodynamics and kinetics, the oxidation products of the alloy during the melting process and the effects of oxidation time and temperature on the oxide layer were analyzed.

The sandstone of the Silurian Xiaoheba Formation in the Sichuan Basin is poorly understood and the exploration prospect is unclear. The geological characteristics of oil and gas from the aspects of sedimentation, reservoir and accumulation of the sandstone of the Xiaoheba Formation in the Sichuan Basin, as well as evaluating its exploration potential and prospect, were made possible using the data on field outcrops, exploratory wells, as well as seismic and logging data. By studying the above, the following four points are understood. (1) The sandstone of the Xiaoheba Formation in the Sichuan Basin is mainly dominated by siltstone. There are two types of sand masses: the distal sandbank sand mass of the foreland basin delta front and the thin layer sand mass intercalated with pro-delta mudstone. The two types of sand masses are widely distributed in east Sichuan. (2) The sandstone reservoir of the Xiaoheba Formation is characterized by low porosity, low permeability and extra density. The late-stage diagenesis led to the densification of the reservoir. Intervals with relatively high porosity were developed locally and satisfactory reservoirs could be developed in the period of reservoir forming. (3) The sandstone reservoir of the Xiaoheba Formation, the high-quality argillaceous hydrocarbon source rocks of the Longmaxi Formation, and the thick layer mud shale caprocks of the Hanjiadian Formation formed a set of high-quality source rocks, reservoir, and caprock accumulation assemblage. The formation and evolution of the Kaijiang paleo-uplift in eastern Sichuan were conducive to the accumulation and preservation of the sandstones of the Xiaoheba Formation. (4) The sandstone of the Xiaoheba Formation is a potential field for natural gas exploration in the Sichuan Basin. Both types of sand masses have a certain potential, among which the favorable exploration area of the sand mass of the distal sandbank is about 10 × 103 km2. The study results are of great significance for improving geological understanding and guiding natural gas exploration in this field.

Well Zhongqiu 1 obtained highly productive oil-gas stream in the footwall of Zhongqiu structure, marking the strategic breakthrough of Qiulitag structural belt in the Tarim Basin. However, the oil and gas sources in Zhongqiu structural belt and the reservoir formation process in Zhongqiu 1 trap remain unclear, so study on these issues may provide important basis for the next step of oil and gas exploration and deployment in Qiulitage structural belt. In this study, a systematic correlation of oil and gas source in Well Zhongqiu 1 has been carried out. The oil in Well Zhongqiu 1 is derived from Triassic lacustrine mudstone, while the gas is a typical coal-derived gas and mainly from Jurassic coal measures. The oil charging in Well Zhongqiu 1 mainly took place during the sedimentary period from Jidike Formation to Kangcun Formation in Neogene, and the oil was mainly contributed by Triassic source rock; large-scale natural gas charging occurred in the sedimentary period of Kuqa Formation in Neogene, and the coal-derived gas generated in the late Jurassic caused large-scale gas invasion to the early Triassic crude oil reservoirs. The Zhongqiu 1 trap was formed earlier than or at the same period as the hydrocarbon generation and expulsion period of Triassic-Jurassic source rocks. Active faults provided paths for hydrocarbon migration. The source rocks-faults-traps matched well in time and space. Traps in the footwall of the Zhongqiu structural fault have similar reservoir-forming conditions with the Zhongqiu 1 trap, so they are favorable targets in the next step of exploration.

The hot-tearing susceptibility of Mg-10Zn-xAl (x = 0, 2, 5, and 7) alloys was studied using constrained rod casting installed with a load cell, thermocouple, and data-management system. Addition of Al content reduced the freezing range and increased the liquid fraction at the end of the primary stage of solidification, during the vulnerable period of alloy solidification. Eutectic healing was observed in alloys containing Al cast at a higher initial mold temperature due to near-equilibrium solidification. Grain refining was confirmed at the microstructural level due to addition of Al. The results also suggested that increasing Al content enabled hot-tearing resistance of Mg-10Zn alloy by facilitating liquid feed for the strain developed during the mid-stage of solidification (0.65Fs to 0.74Fs). Experimental results were compared with Pandat’s simulation results to predict the occurrence of hot tearing in Mg-10Zn-xAl alloys. This indicated that Pandat’s solidification curve could be used to determine the hot-tearing nature of Mg-Zn alloys. The recently proposed hot-tearing criteria of Kou and Clyne–Davie roughly agreed with the experimental results, but did not perfectly predict the influence of different casting conditions.

The effect of Ce content (0–1.6 wt.%) on the modification of Mg2Si phase in the as-cast Mg-5Al-2Si alloy was investigated. The original Chinese script type Mg2Si phase was refined distinctly and transformed to dispersive block shape gradually by adding Ce element. The length of Chinese script type Mg2Si phase was reduced from 110 to 50 μm with increasing Ce content to 1.6 wt.%. The results calculated by Pandat software indicated that the added Ce element first combined with Si to form CeSi2 phase, which could serve as the heterogeneous nucleation of Mg2Si phase due to the small lattice mismatch of 7.97%. The modification of Mg2Si phase was mainly attributed to the facts that Ce changed the growth steps of Mg2Si phase and CeSi2 promoted the nucleation of Mg2Si phase. With increasing Ce content from 0 wt.% to 1.6 wt.%, the YS, UTS and EL at 150 °C were improved from 67.7 MPa, 91.2 MPa and 1.6% to 84.2 MPa, 128 MPa and 7.5%, respectively.

With the increasingly stringent national environmental rules, waste produced in drilling and completion process is forbidden to be discharged into the Bohai Bay or reinjected into the formation. The current disposal method of drilling and completion waste in Bohai Oil field has some problems such as high cost, low efficiency and high HSE management and control risk. Faced with these problems, drilling and completion waste reutilization and zero discharge technology has been developed and applied in this region. In order to reutilize drilling and completion waste which include cuttings circulated from formation, wasted drilling and completion fluids, the following aspects are carried out: Firstly, drilling platform is upgraded to meet the zero discharge requirement: solid control system is modified, cuttings closed transfer system and cuttings treatment system are equipped on the platform to collect and dispose the waste. Meanwhile, recovery and disposal capacity to support different spud drilling are assessed: cuttings transport capacity is up to 15m3/h, which can meet the highest requirements of 12-1/4″ hole drilling when ROP is up to180m/h. Secondly, the well profile is downsized to reduce the production of cuttings, mud and other wastes from the root, which can also improve efficiency and yield cost. The field application shows that the amount of the waste has been reduced by 41.39%, 39.86% and 41.52% in first, second and third spud drilling, and average ROP is 35%, 28%, 42% higher than similar wells drilled before. Lastly, in drilling and completion fluids system optimization and reutilization aspects, environmentally friendly drilling and completion fluids with low solid content are developed. The experiment shows that the properties of the liquid phase after solid-liquid separation can be reused, and the solid phase with low water content is easy to pack and transport back to land. Drilling and completion waste reutilization and zero discharge technology introduced in this paper has been successfully applied in more than 40 wells, and the volume of waste drilling fluid is reduced by 80%, which is a trade-off between zero discharge and well construction cost. This technology can also be applied in other offshore oilfield which is inevitable as the environmental rules become more and more strict.

The effect of second phases on the deformation mechanism of as-cast, solution-treated and aged Mg-7Al-2Sn (AT72) alloys during surface mechanical attrition treatment (SMAT) was investigated. Twinning was suppressed in the alloys containing second phases, which can provide nonuniform microstructures and phase boundaries as dislocation sources. Dynamic precipitation in AT72 alloys was studied during SMAT deformation as well. Mg2Sn particles can dynamically precipitate on the surface of all AT72 alloys during SMAT process. The quantity of Mg2Sn particles in the as-cast alloy, which is determined by the initial quantity of second phases, is larger than that of T4 and T6 alloys after the SMAT process.

The Tugeerming area is located in the eastern part of the Kuqa Depression, Tarim Basin. In recent years, prolific oil and gas flow in the Jurassic Yangxia Formation of Well Tudong 2 indicates broad prospects of exploration in the said area. This paper carries out the oil-gas and source correlation in the Tugeerming area. The findings acquired as briefed as follows. The biomarker characteristics of the crude oil of the Yangxia Formation of the Tugeerming Jurassic group showed that the hydrocarbon precursor types were a typical freshwater source of terrestrial organic matters with in the Yangxia Formation. The natural gas of the group is coal-type condensate with associated gas. The maturity of the natural gas is the same as that of the crude oil, where both of them are derived from the same hydrocarbon source rocks. In this paper, the biomarker comparison technique, n-alkane carbon isotope comparison technique, and kerogen carbon isotope-crude carbon isotope comparison technology system were used to study the Jurassic Yangxia Formation oil in the Tugeerming area, as well as the hydrocarbon source rocks of Jurassic and Triassic in the area. The differences between the source rocks are comprehensive. The results show that there is a maternal relationship between the Yangxia Formation crude oil and the source rocks of the Jurassic Yangxia and Kezilenur formations, which provides an important reference for the evaluation of oil and gas resources in this area. Keywords: Tugeerming area, Jurassic, Triassic, n-alkane carbon isotope, Oil and gas source correlation

The effect of microstructure on thermal conductivity was investigated for Mg-4Ce-xAl-0.5Mn (x = 0 to 6 wt pct) alloys produced by gravity casting and high-pressure die casting. The solidification microstructure of the alloys was quantitatively studied using CALculation of PHase Diagrams (CALPHAD) modeling and experimental characterization. The lattice volume of Mg solid solution was measured via X-ray diffraction (XRD) method. The results show that the thermal conductivity is influenced mostly by lattice volume, and, to a lesser extent, by intermetallic compounds. Also, thermal conductivity has a strong negative correlation with the concentration of total solute atoms. When the addition of Al is less than 3 wt pct, the thermal conductivity of die casting alloys with higher cooling rate and solute concentration is lower than that of gravity casting alloys. However, their thermal conductivities tend to be equal when the Al addition exceeds about 3 wt pct, as the concentration of solute atom is approaching the solid solubility limit. Two methods (structural model and Wiedemann–Franz law) were proposed and modified to predict their thermal conductivities, respectively. Both can provide a good prediction of thermal conductivity values.

The 7th generation semi-submersible drilling units (CSDU) are characteristic of deeper drilling depth, site locations and higher operational efficiency, compared with the last generation ones. Given the enormous live loads change and increasing trend of main size dimensions, considerable optimization should be deployed to achieve a balance of economy, safety and good work performance. Trial calculation and definite assessment to check whether alternative schemes meet the requirements turns out to be ineffective, for the case by case study of hydrodynamic and structure strength analysis is time consuming. In the paper, an integrated optimal design model is formulated by merging multi-objective optimization and multi-attribute decision making into one. A predesigned parametric Finite Element Analysis (FEA) structural model of CSDU is developed and validated and then coupled with detailed hydrodynamic analysis. Three mutually conflicting design objectives are arrived by hydrodynamic solutions. They are stability, hydrodynamic performance and steel consumption, which are screened to obtain Pareto optimality. The Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) is applied to incorporate these optimal attributes into decision-making process, considering all criteria in terms of quantitative stability, hydrodynamic performance and qualitative economy. The objective entropy coefficient measuring the importance of different attributes is introduced into weight selection for the purpose of avoiding non-determinacy and optional judgements. The optimal solutions are further verified with main dimensions of CSDUs in service and also could give predictive suggestion for the new CSDUs. The study provides a more objective way of benchmarking different structural schemes of CSDU by considering multiple criteria simultaneously. It is demonstrated that the proposed structural optimization model is capable of effectively and accurately determining the optimal design of CSDU.

Generalized stacking-fault energies (GSFEs) of basal-plane stacking faults I1 and I2 in Mg alloys have been studied based on first-principles calculations, where 43 alloying elements were considered. It is found that the most contributing features of alloying elements to GSFEs are bulk modulus, equilibrium volume, binding energy, atomic radius and ionization energy. Both bulk modulus and ionization energy exhibit positive relationships with GSFEs, and the others show opposite relationships. Multiple regressions have been performed to offer a quantitative prediction for basal-plane GSFEs in Mg-X systems. GSFEs, alloying effects of elements and the prediction model established within this work may provide guidelines for new Mg alloys design with better ductility.

The influences of solute atoms (Li, Al, Mn, Zn, Fe, Ni, Cu, Y, Zr) and Cl adsorption on the anodic corrosion performance on Mg (0001) surface have been investigated based on first-principles calculations, which might be useful for the design of corrosion-resistant Mg alloys. Work function and local electrode potential shift are chosen as descriptors since they quantify the barrier for charge transfer and anodic stability. We found that at 25% surface doping rate, Y decreased the work function of Mg, while the impact of remaining doping elements on the work function of Mg was trivial due to the small surface dipole moment change. The adsorption of Cl destabilized the Mg atoms at surface by weakening the bonding between surface Mg atoms. We find that a stronger hybridization of d orbits of alloying elements (e.g. Zr) with the orbits of Mg can greatly increase the local electrode potential,which even overbalances the negative effect introduced by Cl adsorbates and hence improves the corrosion resistance of Mg alloys.

Arc-soft-toe bracket (ASTB), as a joint structure in the marine structure, is the hot spot with significant stress concentration, therefore, fatigue behavior of ASTBs is an important point of concern in their design. Since macroscopic geometric factors obviously influence the stress flaws in joints, the shapes and sizes of ASTBs should represent the stress distribution around cracks in the hot spots. In this paper, we introduce a geometric magnification factor for reflecting the macroscopic geometric effects of ASTB crack features and construct a 3D finite element model to simulate the distribution of stress intensity factor (SIF) at the crack endings. Sensitivity analyses with respect to the geometric ratio H t /L b , R/L b , L t /L b are performed, and the relations between the geometric factor and these parameters are presented. A set of parametric equations with respect to the geometric magnification factor is obtained using a curve fitting technique. A nonlinear relationship exists between the SIF and the ratio of ASTB arm to toe length. When the ratio of ASTB arm to toe length reaches a marginal value, the SIF of crack at the ASTB toe is not influenced by ASTB geometric parameters. In addition, the arc shape of the ASTB slope edge can transform the stress flowing path, which significantly affects the SIF at the ASTB toe. A proper method to reduce stress concentration is setting a slope edge arc size equal to the ASTB arm length.

In this study, the room temperature thermal conductivity and microstructure of Mg−Ce, Mg−Sm and Mg−Y binary alloys in as-cast and solution treated conditions were investigated. Quantitative study was conducted on the effect of rare earth elements (in solid solution and intermetallic compounds) on the thermal conductivity of Mg−RE alloys. The reduction in thermal conductivity was determined to be about 123.0 W/(m·K) and 6.5–16.4 W/(m·K), respectively, per 1 at.% RE addition in the form of solid solution or intermetallic compounds with Mg. The thermal conductivities of Mg−RE alloys were fitted using modified Maxwell and EMT models based on the distribution, volume fractions and shape of intermetallic compounds. The modified structural models provide a good fit to the experimental thermal conductivity data.

Graphene (graphene) is a new type of two-dimensional inorganic nanomaterial developed in recent years. It can be used as an ideal inorganic nanofiller for the preparation of polymer nanocomposites because of its high mechanical strength, excellent electrical conductivity and plentiful availability (from graphite). In this review, the preparation methods of graphene/polymer nanocomposites, including solution blending, melt blending and in situ polymerization, are introduced in order to study the relationship between these methods and the final characteristics and properties. Each method has an influence on the final characteristics and properties of the nanocomposites. The advantages and disadvantages of these methods are discussed. In addition, a variety of nanocomposites with different properties, such as mechanical properties, electronic conductivity, thermal conductivity and thermal properties, are summarized comprehensively. The potential applications of these nanocomposites in conductive materials, electromagnetic shielding materials, photocatalytic materials and so on, are briefly presented. This review demonstrates that polymer/graphene nanocomposites exhibit superior comprehensive performance and will be applied in the fields of new materials and novel devices. Future research directions of the nanocomposites are also presented.

Developing simple and selective methods for formaldehyde (FA) detection are of great interest, because FA is not only an environmental pollutant, but also an endogenous bioactive molecule. Herein, a new ratiometric fluorescent probe (HBT-FA) based on aza-Cope reaction was designed and synthesized, which showed high selectivity and ratiometric fluorescence response to FA. Furthermore, the probe could detect FA in various medium, such as aqueous solution, serum and air.

As a new class of fluorescent carbon materials, graphene quantum dots (GQDs) have attracted tremendous attention due to their outstanding properties and potential applications in biological, optoelectronic, and energy-related fields. Herein, top-down and bottom-up strategies for the fabrication of GQDs, mainly containing oxidative cleavage, the hydrothermal or solvothermal method, the ultrasonic-assisted or microwave-assisted process, electrochemical oxidation, controllable synthesis, and carbonization from small molecules or polymers, are discussed. Different methods are presented in order to study their characteristics and their influence on the final properties of the GQDs. The respective advantages and disadvantages of the methods are introduced. With regard to some important or novel methods, the mechanisms are proposed for reference. Moreover, recent exciting progresses on the applications of GQD, such as sensors, bio-imaging, drug carriers, and solar cells are highlighted. Finally, a brief outlook is given, pointing out the issues still to be settled for further development. We believe that new preparation methods and properties of GQDs will be found, and GQDs will play more important roles in novel devices and various applications.

We developed a facile and effective route to synthesize GQDs for bioimaging by using starch as a precursor. The reactants consist of only starch and water. Furthermore, the products are only GQDs, water, and carbide precipitate. Thus, the complicated post-processing steps are avoided. The present work is the first report of the synthesis of GQDs from a high molecular weight polymer.

Microstructure evolution of a supersaturated solid solution Mg–2.2 wt%Nd alloy during aging at 240 °C for 6 h (stage I), at 295 °C for 3 h (stage II), and finally at 320 °C for 1 h (stage III) was studied by in situ synchrotron X-Ray diffraction. In stage I, diffraction from β 1 (Mg 3 Nd, FCC) precipitates was observed after ~ 15 min. Evolution of the volume, size, and aspect ratio of β 1 with the aging time were estimated from peak intensity and peak width analysis. In stage II, diffraction from β (Mg 12 Nd, tetragonal) precipitates was observed after ~ 36 min while β 1 remained in the material. In stage III, the volume of β 1 reduced substantially in relative to β . The identified precipitation sequence from the in situ aging experiment is supported by ex situ electron microscopy observations. β ′, which had not been detected by synchrotron X-rays, was additionally found using transmission electron microscopy in the material by the end of aging stage I. Tension and hardness tests using specimens with different aging conditions were further performed to understand how different precipitates affect the strength and ductility of the Mg–Nd alloy.