- Ei，ESCI收录期刊
- 中国科学引文数据库(CSCD)核心期刊
- 中文核心期刊
- 文摘与引文数据库(Scopus)
- 剑桥科学文摘(CSA)
As a novel 2D carbon material featuring high electrical conductivity, large specific surface area and remarkable chemical stability, graphene has shown its promising potentials in the field of photocatalytic technology. The recent research progress in graphene along with its composites as photocatalysts for environmental purification was reviewed. The photocatalytic mechanism and the exceptional properties of graphene were briefly introduced, and the fundamental roles of graphene played in the photocatalytic composites were well summarized, including facilitating the transport of photogenerated electrons, amplifying the intensity and expanding the range of light adsorption, and enhancing absorption capacity. A variety of graphene-based photocatalytic composites (graphene/inorganic semiconductors, graphene/organic semiconductors and graphene/metal nanoparticles) as well as their synthesizing routes was grouped by categories and reviewed respectively. The applications of graphene-based photocatalytic materials in the field of environmental purification were introduced systematically, which were mainly focused on the air purification, water decontamination of trace pollutants and wastewater treatment. Finally, it was pointed out that the graphene-based photocatalytic materials still have some problems, such as low catalytic efficiency, high cost, difficulty in realizing large-scale production and so on. The optimization of their structure, preparation technology and other parameters is expected to improve the materials properties and enhance their practical application value.
The rise of the era of 5G wireless technology and development of flexible electronic devices have highlighted the key role of electromagnetic shielding materials for national defense and civil use. As a new carbon material, graphene has a unique two-dimensional structure showing excellent physical and chemical properties, which endows graphene-based materials light weight, good flexibility, high corrosion resistance and high electromagnetic shielding effectiveness. The shielding principle and the preparation method of graphene-based material were introduced in this review, and the latest advances on the electromagnetic shielding material were summarized, including pure graphene and graphene-based composite material. In addition, prospects for the future development of new graphene-based electromagnetic shielding materials were discussed.
The mass production of graphene sheets is a prerequisite for exploiting the applications of graphene. A major focus of experimental research has been concentrated on the development of effective approaches to produce well-defined graphene in large scale. Due to its high yield and cost efficiency, chemical reduction of graphene oxide has been proofed to be one of the most feasible approaches to achieve this goal. Graphene consists almost entirely of sp2 hybridized carbon atoms, while graphene oxide additionally contains sp3 regions, oxygen functional groups and structural defects. The fundamental understanding of the mechanism of chemical reduction of graphene oxide is a key issue when preparing graphene materials via graphene oxide precursor. Although dozens of methods have been exploited to facilitate the chemical reduction of graphene, only few studies were focused on the reduction mechanism.The chemical reduction strategies of graphene oxide, and as well as their mechanisms were reviewed in this paper. It was suggested that the core issue of the reduction is how to clarify the removal of hydroxyl groups and the simultaneous restoration of a conjugated structure.
Due to its one-atom thickness, excellent optical and electrical properties, graphene has great potential applications in fields of transistors, solar cells, supercapacitors and sensors. For further development of practical applications, controllable synthesis of high-quality graphene is of great importance.Because of its advantage in in-situ growth on various substrates at low temperature, plasma-enhanced chemical vapor deposition(PECVD) has become one of the most promising strategies for the synthesis of graphene in the future. In this paper, the effect of several key factors on the growth of graphene by PECVD, such as plasma power, temperature, substrates and pressure was summarized. Two growth mechanisms including nucleation and coalescence mechanism and etching and edge growth mechanism were reviewed. Furthermore, the challenges and development of graphene were also discussed. In future work, the controllable preparation of graphene on the nucleation and growth of graphene will be essential to achieve large-area and high-quality graphene by PECVD at low temperature, laying the foundation for the application of graphene synthesized by PECVD in electronics and other fields.
Raman spectroscopy is well-known for its capability of detecting the physical properties, level of defects and number of layers for graphene-based materials, but far more than that, it's proven to be a versatile and promising tool for characterizing graphene-based polymer composites. This work focuses on the applications of Raman spectroscopy in the field of graphene-based polymer composites. The feature bands in Raman spectroscopy enable direct 2D and 3D imaging of graphene-based nanofillers in the polymer matrix, and even out of other carbonaceous materials. In addition, shifts in the vibrational frequencies of the characteristic bands induced by the strain of graphene could be utilized for analyzing the interactions between graphene-based nanofillers and polymer molecules, for calculating the effective moduli as well as for determining the spatial orientation of graphene-based nanofillers in the matrix. In the meantime, the recent progress of applications of Raman spectroscopy in the field of graphene-based polymer composites is introduced, such as the analysis of micromechanics of graphene-based nanocomposites, the investigation of stress transfer efficiency between the nanofillers and the matrix, and the reveal of key factors affecting material behavior. The Raman spectroscopy researches of graphene-based polymer composites currently are mainly focused on model composites, and the fluorescent effect of the matrix polymer as well limits the further applications of Raman spectroscopy. In order to address such problem, the amplified razor power are often adopted, and the resulted nonlinear effects are capable of increasing the intensity of the Raman signal, thus the Raman spectroscopy will be more widely applied in the field of graphene-based polymer composites.
Pearlite transformation and its re-austenitization process, which involve triple phases and dual phase interfaces, have been considered difficult phase transformation processes. Thus, the mechanism and physical nature of them are waiting to be studied. The partition of carbon and substitutional alloying element M during transformation by integrating the previous results were clarified. Moreover, the application of phase field method in the pearlite transformation was introduced. Based on the large amount of the experimental and calculated results, the influence of the inhomogenous microstructure and composition on the re-austenitization from pearlite were further discussed. Partitional and non-partitional transformed temperature (PNTT), which is due to the large difference of diffusion coefficient between C and M, was further studied. Based on this, a new heat treatment of near-eutectoid Mn-contained steel has been put forward. The segregation of Mn in retained austenite can be significantly improved compared to the traditional Q&P treatment, and then the stability of the retained austenite can be enhanced and the guidance can be provided for controlling the martensite/austenite dual phase microstructure more systematically.
Membrane is the basic material in the area of numerous modern separation and energy generation processes. Among various kinds of membranes, Janus membrane, the name of which comes from the ancient Roman mythology that the god exhibits two faces, exhibits superior properties to homogenous membranes by reason of its asymmetric morphology or chemical composition on its two sides. In recent years, with the further exploration and development of Janus membranes, the design, fabrication of Janus membranes and their application in many fields have attracted widespread attention. Herein, the common categories and fabrication of Janus membranes were reviewed. The progress of Janus membranes in unidirectional liquid penetration, oil-water separation and desalination was summarized. Finally, the current challenges in the preparation strategies of Janus membrane were pointed out, such as the different membrane thicknesses required in different application fields, how to achieve the accurate control of the thickness. Meanwhile, the development trend of Janus membrane in oil-water separation, fog collection was prospected.
The basic structure, working principle, and the development process and research status of resistive random access memory (RRAM) were outlined. Material systems, including dielectric materials, electrode materials, and substrate materials, as well as broad trends and recent researches of flexible RRAM were summarized; the performance characteristics of flexible RRAM, including storage performance and mechanics performance, were analyzed. The significance and challenge of developing flexible RRAM were explicated. Problems existing in this area and possible approaches to the problems were also put forward. It was concluded that the highly conductive stretchable electrode and the steadily stored stretchable dielectric are primary direction in the future.
Magnetic nanomaterial has been widely used in water treatment due to its high biocompatibility, good adsorption performance, and easy solid-liquid separation. In this paper, the classification, common form, and functional methods of iron-based magnetic nanocomposites as adsorbents to remove heavy metal ions were summarized. The functional principle of iron-based magnetic nanoparticles and the adsorption mechanism of these materials in adsorption process were discussed. In addition, the unsolved problems, include the agglomeration, oxidation, and unstability of iron-based magnetic nanomaterial applied in wastewater treatment were analyzed. Finally, the functionalization on the iron-based magnetic nanomaterial for the removal of heavy metal ions was prospected, which provides more adequate theoretical basis for heavy metal ions in wastewater treatment.
The enhanced electrochemical performance of the lithium-rich solid solution Li1.2[Co0.13Ni0.13Mn0.54]O2 (LMNCO) cathode was enhanced by phosphorus incorporation. The various phosphorus contents were introduced by adding NH4H2PO4 into the raw materials. The pristine sample and the sulfur incorporated samples were characterized by X-ray diffraction(XRD), high resolution transmission electron microscopy(HRTEM), electrochemical impedance spectroscopy(EIS). Electrochemical performance was assessed by measuring parameters such as charge and discharge capacity, rate capability in lithium ion cells. The results show that the LMNCOP-03 material has the best initial discharge capacity of 280 mAh·g-1. Moreover, it has about 212.2 mAh·g-1 and 170.6 mAh·g-1 at 1.0 C and 3.0 C rate, respectively. The LMNCOP-03 material shows an improved rate performance attributed to the enhanced electrical conductivity and lithium ion diffusion, which is proved by EIS tests.
Induction cladding TiB/Ti composite coating was in-situ synthesized by induction heating the preplaced powder mixture of 90% Ti (atom fraction, the same below) and 10% boron on a Ti6Al4V substrate. The microstructure, phase composition and micro/nano mechanical properties of the coating were studied by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), microhardness tester and nanoindentation tester. The results indicate that the composite coating has a smooth surface and a dense microstructure without cracks and pores. A strong metallurgical adherence is formed between the coating and the substrate. During induction cladding process, B and Ti are fully reacted to in-situ form TiB reinforcements. The matrix of the coating consists of α-Ti phase and a few β-Ti phases. The reinforcements of in-situ synthesized TiB are uniformly distributed in the coating with a volume fraction about of 9.4%. Indentation hardness and modulus of the in-situ TiB particles are about 35 GPa and 545 GPa, respectively, which cause the increase of the microhardness of the composite coating to about 525HV0.2. It is increased by 67% as against the Ti6Al4V substrate.
Titanium/steel laminated composite plates were prepared by cold rolling method. The effects of rolling reduction, rolling speed, surface roughness, state of raw material and rolling pass on the interfacial bonding strength of titanium/steel laminated composite plates were studied. The results show that the interfacial action force and action time of rolling force on the interface are the main parameters affecting the interfacial bonding strength of titanium/steel laminated composite plates. The rolling reduction, surface roughness and state of raw material affect the interfacial bonding strength of titanium/steel laminated composite plate through affecting the interfacial action force. The rolling speed affects the interfacial bonding strength of titanium/steel laminated composite plate through affecting the action time of rolling force on the interface. Whether the titanium/steel laminated composite plate can be cold roll bonded or not has nothing to do with the number of rolling passes, only when the rolling reduction of single pass exceeds the critical rolling reduction can the cold roll bonded be realized.
The thermophysical simulation of a new wrought superalloy GH4066 was carried out by Gleeble-3800. The high temperature flow stress characteristics of this material under different deformation conditions such as the temperature of 800, 900, 1000, 1100℃ and 1150℃, and the strain rate of 0.0003, 0.001, 0.01, 0.1, 1, 10 s-1 were obtained. Based on the experimental data and the phenomenological model, the constitutive model of the material was established. The dynamic recrystallization and grain growth model of the material were also obtained. All the models are embedded into the finite element software to simulate the forging process of the turbine disc made by this material. As the numerical simulation results, the reasonable range of the thermoforming parameters for the turbine disk can be concluded.Finally, the material models are verified and an integrated method of experiment and calculation for the material models construction are established. That is a quite useful method for the parameters determination for the turbine disk forging process of this new material.
It is very important to apply an effective method to predict the crystallization degree of laser 3D printed bulk metallic glasses (BMGs) for selecting and optimizing the processing parameters of laser 3D printing. In the present study, beginning with the kinetics of crystallization of amorphous alloys, the crystallization activation energy and Arrhenius factor were obtained by testing the characteristics of the temperature of the amorphous alloy under different heating rates, then a novel method of predicting the volume fraction of crystallization for the metallic glass produced by laser 3D printing was proposed combined with the finite element simulation technology. The validity of the method was verified by using Zr50Ti5Cu27Ni10Al8(Zr50) amorphous alloy as the model system. The result shows that the volume fraction of the crystalline phase of the single-track Zr50 BMG obtained by this method is 1.23%, which is very close to the experimentally obtained crystallization phase volume fraction of 1.65%. This strongly proves the effectiveness of the theoretical prediction method for the crystallization volume fraction of laser 3D printing BMGs.
At the conditions of 760℃/800 MPa, 980℃/250 MPa and 1100℃/137 MPa, the transv-erse stress rupture properties of a nickel-based third generation single crystal superalloy were investigated. The results show that the stress rupture life and elongation of the transverse specimens are lower than those of the longitudinal specimens at 760℃/800 MPa, 980℃/250 MPa and 1100℃/137 MPa. The dislocation configurations of the stress ruptured transverse and longitudinal specimens are the same. There are intersecting stacking faults in the γ' phases after stress ruptured at 760℃/800 MPa, and the dislocations are tangled and high densities of dislocation networks have formed at the γ/γ' interface after stress ruptured at 1100℃/137 MPa. The transverse and longitudinal specimens show quasi-cleavage and dimple mixture mode at 760℃/800 MPa, while they both show dimple mode at 980℃/250 MPa and 1100℃/137 MPa. The fracture mechanisms of transverse specimens of the first generation single crystal superalloy DD3, the second generation single crystal superalloy DD6 and the third generation single crystal superalloy in our study at medium and elevated temperatures are basically the same. The main reason for the transverse specimens have a lower stress rupture properties than the longitudinal specimens is that the external applied stress is perpendicular to the primary interdendritic interface formed during the directional solidification process.
Tribological properties of oleic acid modified natural serpentine ultrafine mineral powders as lubricating oil additive were investigated by a reciprocating sliding wear tester. The effects of the four factors including load, reciprocating frequency, sliding time and concentration of serpentine on the properties of serpentine additive were analyzed. Results indicate that the anti-wear and friction-reducing properties of the base oil are significantly improved by the addition of the modified serpentine powders. The order that affects the friction-reducing performance of the serpentine additive is:concentration, reciprocating frequency, load, sliding time, and the optimal tribological conditions are 100 N, 5 Hz, 180 min, 0.5%(mass fraction). While that affects the anti-wear property is:load, concentration, reciprocating frequency, sliding time, and the optimal conditions are 100 N, 50 Hz, 180 min, 0.3%. Serpentine minerals forms a tribofilm consisting of various oxides, graphite and organic compounds on the friction surface, which is the key to improving anti-wear and friction-reducing properties.
The T700/HT280 composites were subjected to vacuum thermal cycling (-140-180℃, 10-3 Pa). The mass loss rate, dynamic mechanical properties and low-speed impact of composites were tested before and after vacuum thermal cycling respectively. The visual observation, ultrasonic C-scan and finite element (FE) analysis were used to analyze, characterize and simulate the low-speed impact damage. The results show that the mass loss rates of T700/HT280 composites and matrix resin are increased rapidly and then level off with the increase of the number of vacuum thermal cycles, which is due to the gassing effect. After the vacuum thermal cycle treatment, T700/HT280 composites show some degree of post-cure, thermal aging and partial interface debonding. The main damage mode at low impact energy is that the matrix resin is compressed. However, matrix cracking and delamination are deemed as the damage mode at high impact energy. The FE simulation results are consistent with the experimental results. As the impact energy increases, the absorption energy of the composites is increased. Under the condition of 30-40 J impact energy, the absorption energy can effectively characterize the environmental damage effects of vacuum thermal cycle on composites.
Superhydrophobic coatings with micro-nano hierarchical structure constructed by nano particles usually have a poor behavior in water impact situation. This weakness limits superhydrophobic coatings' outdoor potential applications. A low-acoustic resistance all-organic superhydrophobic coating was prepared by spraying and compression molding methods with epoxy and PTFE particles. Water impact test was designed according to impact failure mechanism, and then water impact resistance was evaluated and compared with commercial superhydrophobic coatings'. The results indicate that the hydrophobicity reaches peak when coating contains 70% (mass fraction, the same below) PTFE particles, with 164.13° water contact angle(WCA) and 3° water slide angle(WSA). For water impact resistance, the coating with 75% PTFE particles has the best performance, it can keep the WCA at 154.62° after 22.77 ms-1 water jet impact test. And the molding coatings have better performance than sprayings. Besides, the results also show coating's good adhesion and wearability, for example, it can keep the WCA at 150.51° and WSA at 4° after 25-cycle tape peeling test, and keep the WCA at 149.21° and WSA at 9° after 20-cycle wear test.
In order to solve the problem that alumina based ceramic core is not easy to remove core, a certain amount of PA66 fiber was added as pore forming material to prepare porous aluminum based ceramic core by hot pressing. The influence of PA66 fiber content on the porosity, room temperature bending strength and sintering shrinkage of aluminum based ceramic core was investigated, and the mechanism of PA66 fiber content on the porosity of aluminum based ceramic core was analyzed. The results show that the porosity of alumina based ceramic core is significantly increased by adding PA66 fiber, and the sintering shrinkage of the core is effectively blocked. With the increase of PA66 fiber, the porosity of alumina based ceramic core is increased, and the bending strength and line shrinkage rate at room temperature are decreased. When the PA66 fiber content is 0.9%(mass fraction), the porosity of the aluminum based ceramic core is 41.14%, the bending strength is 15.33 MPa, and the linear shrinkage rate is 0.418%.
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