三元层状结构MAX相陶瓷材料的制备技术及其研究发展现状和发展趋势

三元层状结构陶瓷材料主要是指M_n+1AX_n相,三元层状结构MAX相陶瓷材料具有金属的特性还具有陶瓷的特性,三元层状结构MAX相陶瓷材料具有较高的力学性能,良好的耐磨损性能和良好的耐腐蚀性能,并具有良好的抗高温氧化性能等,还具有良好的可加工性能。三元层状结构MAX相陶瓷材料主要有Ti₃SiC₂,Ti₄SiC₃,Ti₃AlC₂,Ti₂AlC,Ti₄AlN₃和Ti₂AlN等。本文主要叙述三元层状结构MAX相陶瓷材料的制备技术,物相组成,显微结构,力学性能和耐磨损性能,耐腐蚀性能和抗高温氧化性能以及其他性能等。并叙述三元层状结构MAX相陶瓷材料的研究发展现状和发展趋势。并对三元层状结构MAX相陶瓷材料的未来研究发展趋势和发展方向进行分析和预测。     

Fracture Toughness Enhancement for Alumina Systems: A Review

Investigations have been carried out to determine ways of tailoring ceramic materials in order that one or more toughening mechanisms are activated in service. Microstructural manipulations, as well as composite formulations involving metallic, intermetallics, and ceramic phases have been used with ceramic matrices. Macrostructurally, laminated structures and functional gradient materials (FGMs) have also been formulated to enhance mechanical properties. Although significant improvements in material properties have been reported, ceramics are still below their projected positions on the materials map. This article presents a review of research activities pursuant to improving fracture toughness of alumina matrix systems and the enhancements achieved.     

High-temperature carbothermal synthesis and characterization of graphite/h-BN bimaterials

Hexagonal boron nitride (h-BN) and graphite have similar crystal structures, comparable lattice parameters, and coefficients of thermal expansion, but vastly different electrical and thermal transport. Despite their key differences, it is possible to couple h-BN and graphite in a bimaterial system allowing the unique properties of both materials to be utilized in a single component. Through a carbothermal reduction of B₂O₃ in nitrogen, the surface of graphite can be converted to h-BN. This results in a layered system that is electrically insulating on the surface due to h-BN, and more compliant as well as conductive within the substrate due to the graphite structural body. We discuss the high-temperature synthesis and characterization of this layered material, focusing on the processing–microstructure relationship as well as the interface of graphite/h-BN to assess the chemical and mechanical adhesion of the layers, and to establish how such properties are contingent on the reacting phase of B₂O₃. This is achieved by investigating the origin of h-BN formation and the unwanted side reaction of boron carbide formation, through the evaluation of the thermochemistry and kinetics governing the carbothermic reactions. We establish that a reaction temperature and holding time of 1700°C for 18 h produced the thickest h-BN layers which exhibited the highest fracture toughness over all lower temperature synthesis conditions.     

Comparative Review on Structure,Properties, Fabrication Techniques,and Relevance of Polymer Nanocomposites Reinforced with Carbon Nanotube and Graphite Fillers

Owing to their remarkable electrical, mechanical, thermal, catalytic, and optical properties as well as their unique structure, carbon nanotubes and graphite have been exploited to produce high performance and multifunctional composites. The resultant composites are differentiated on the basis of their properties to meet various applications. In the framework of this review article, we have mainly focused on the preparation, structure, and properties of two families of composite materials with an emphasis on the differences between them. Moreover, the current challenges, future prospectives, and applications of carbon nanotubes- and graphite-based materials in sensors and in photovoltaic and energy storage devices (Li-ion battery) have been discussed.     

三元层状可加工导电MAX相陶瓷研究进展

三元层状可加工导电陶瓷是一类键合具有明显各向异性的层状碳化物或氮化物,它通常又被称为MAX相陶瓷。MAX相陶瓷具有优良的可加工性,良好的导电、导热能力,可观的高温强度,同时还具有良好的热稳定性、抗氧化性、抗热震性和耐腐蚀性能。本文介绍了MAX相陶瓷的结构、性能以及制备方法和应用前景。     

A review of strategies for improving the degradation properties of laminated continuous-fiber/epoxy composites with carbon-based nanoreinforcements

Continuous-fiber/epoxy-matrix laminated composites are a key structural material for aeronautical and aerospace applications. Introducing nanoscale reinforcements to these materials is a possible way to achieve improved mechanical properties. To date, much work has been done on nano-reinforced polymers. However, few systematic studies concerning the effect of the nanoreinforcements on the mechanical properties on laminated composites were conducted. This paper presents a systematic review of the mechanisms of degradation in laminated structures and considers various nanoreinforcement strategies in the light of well-known mechanisms of degradation and phenomenologies in classical laminated composites. We also discuss various nanoreinforcement strategies in terms of their potential to reduce degradation on every scale. In addition, we review studies conducted on the role that nanoreinforcements play in mechanical properties involved in structural simulation and design. The degradation mechanisms are systematically considered to provide a full picture of each reinforcement strategy.     

Preparation of TiC/Ti2AlC coating on carbon fiber and investigation of the oxidation resistance properties

MAX phases were proposed as the interphase materials for carbon fiber reinforced ceramic matrix composites toward the applications in high‐dose irradiation and oxidation environments. A thickness‐controllable TiC/Ti₂AlC coating was fabricated on carbon fiber using an in situ reaction in a molten salt bath. The coating showed a multilayered structure, in which the inner layer was TiC and the outer layer was Ti₂AlC. The influence of the reaction conditions on the morphology, composition, and thickness of the coating was investigated. The oxidation resistance properties of the as‐prepared TiC/Ti₂AlC‐coated carbon fiber in static air and water vapor flow at elevated temperatures were investigated. The results showed that the as‐prepared TiC/Ti₂AlC coating could provide good protection to the carbon fiber in both static air and water vapor flow up to 800°C. As these TiC and Ti₂AlC materials have good irradiation resistance, the present work provides a potential way to develop an irradiation‐resistant interphase of carbon‐fiber‐reinforced ceramic matrix composites for nuclear applications. Furthermore, this work also provides a feasible way to prepare carbide/MAX phase coating on other carbon materials.     

Green and efficient production of boron nitride nanosheets via oxygen doping-facilitated liquid exfoliation

As the structural analogue of graphene, boron nitride nanosheets (BNNSs) are anticipated to have a wide range of potential applications. BNNSs exhibit good mechanical properties, outstanding thermal conductivity, oxidation and chemical stability and are excellent electrical insulators. While BNNSs have gained recognition as one of the most versatile 2D materials in recent years, their application in research and industry is still hampered by the lack of methods to produce BNNSs in large quantity and a cost-effective way. In this study, we report highly efficient h-BN exfoliation via the oxygen doping-facilitated liquid exfoliation. Oxygen atoms are introduced into the hexagonal boron nitride (h-BN) structure via a facile thermal treatment. The relationship of thermal treatment, structural changes and h-BN exfoliation are studied to elucidate the key factor for advancing the BNNS production. The optimum concentration of hydroxyl groups and weakening of interlayer interactions have synergistically facilitated the delamination of h-BN in water under mild exfoliation conditions, resulting in up to 1255% yield increment and without noticeable new defects in the BNNS structure as compared with the untreated control. An efficient and environmentally friendly exfoliation process of h-BN is a crucial starting point towards the cost-effective and mass production of BNNSs which is needed for the currently identified and myriad future applications of BNNSs.     

Phase-field simulation of microscale crack propagation/deflection in SiCf/SiC composites with weak interphase

To understand the microscale toughening mechanism, the crack propagation, and stress–strain response of unidirectional SiC_f/SiC composites with h-BN interphase under transverse and longitudinal tension are investigated by a promising micromechanical phase field (PF) method along with representative volume element. Of much interest, the calculation results are well consistent with the available experimental results. With a strong dependence on the interphase strength, the toughening mechanisms during crack propagation are well presented, for example, fiber pull-out, crack deflection, and interphase debonding. Furthermore, the longitudinal tensile strength of SiC_f/SiC composites increases with decreasing the interphase strength, where only a weak enough interphase can result in a significant crack deflection by its cracking. In particular, the ratio of the interphase strength along fibers to the matrix strength should be less than 1.254 to ensure crack deflection in the interphase and fiber pull-out. Moreover, the transverse tensile strength of SiC_f/SiC composites reaches a maximum with increasing the interphase thickness into the range of 0.25–0.5 µm.     

Processing of MAX phases: From synthesis to applications

MAX phases are a large family of materials with more than 150 different compositions that have been extensively investigated during the last 25 years. They present a layered structure and a unique combination of properties, bridging the gap between metallic and ceramic properties. However, despite their excellent response of some compositions at high temperature—excellent oxidation resistance up to 1400°C under corrosive environment, good damage and radiation tolerance, thermal shock resistance, and self-crack healing—their transfer to applications has been limited by three main factors: i) complexity of this large family of materials, ii) unavailability of highly pure commercial powders, and iii) extensive time to license products in strategic fields such as nuclear or aviation. In this article, the main properties and synthesis routes are reviewed, including solid state reaction methods, physical vapor deposition (PVD) techniques and molten salt processes. Emphasis is given to processing routes for developing different structures such as dense bulk samples, ceramic matrix composites, foams with different porosity, coatings by PVD and thermal spray technologies, and near net shaping by slip casting, injection molding, and additive manufacturing. Well-known and novel potential applications are described such as structural materials for high temperature applications, protective coatings and bond-coats for gas turbines, accident tolerant fuel cladding in nuclear power plants, solar receiver in concentrated solar power systems, electrical contacts, catalyst, and joining material. Finally, high impact investigations and future challenges are listed in order to facilitate the transfer of MAX phases to the market.     

延性夹层层状陶瓷复合材料的研究进展

延性材料作为层状陶瓷复合材料的一种典型夹层材料,对层状陶瓷复合材料性能的提高具有独特的作用。本文从层状结构设计和制备、增韧机理、研究现状,以及存在的问题和发展前景等方面,对近年来采用延性金属和有机树脂作为夹层材料制备的层状陶瓷复合材料进行了综述。     

Effects of cross-scale h-BN grains and orientation degree on the mechanical and thermal properties of BN-matrix textured ceramics

h-BN is a two-dimensional ceramic material with a lamellar structure, known for its typical orientation characteristics on mechanical and thermal properties. By optimizing the size and arrangement of h-BN grains in the matrix, the anisotropic characteristics of h-BN ceramics can be fully utilized to obtain ceramic materials with high thermal conductivity or high strength. In order to study the effect of grain orientation distribution on the mechanical and thermal properties of materials, the index of orientation distribution (IOP) was used to quantitatively characterize the orientation degree of h-BN grains and analyzed the effect of h-BN grain size on material properties. The results show when the initial h-BN size is 13.50 μm, the ceramic has the highest orientation degree/-507, and the mechanical and thermal properties show obvious anisotropy. While the related properties of BN-YAG ceramics varies significantly with the decrease of initial h-BN grain size.     

Evolution from graphite to graphene elastomer composites

Elastomer composites have established a unique position among technologically important materials because of their extensive and potential applications. Considerable interest has been devoted to graphite derived elastomer composites, known as new generation materials, due to their exceptional electrical, mechanical and permeability properties. The discovery of graphene opened a promising aspect towards the synthesis of elastomer nanocomposites. A thorough investigation of the properties of various graphitic fillers, such as natural graphite flakes, expanded graphite (EG), graphite nanoplatelets (GNP) and graphene is undertaken in this review. The dependence of these fillers on the rheological, electrical (sensing), mechanical, thermal, dielectric and barrier properties of elastomer composites is discussed, giving special emphasis to particle size and mode of interactions with the matrix. A systematic evolution from microcomposites to nanocomposites is shown to give definitive evidence of the importance of graphene nanocomposites. Most preparation methods of these composites are covered, including, solution blending, latex compounding, in situ polymerization, and melt intercalation. Graphene exhibits very good dispersion in most elastomers and substantially improves the mechanical and electrical properties of the matrix compared to all other graphite derivative composites. A review of the potential applications of these composites and current challenges is provided in order to guide future progress on the development of more promising materials.     

The reduction of graphene oxide

Graphene has attracted great interest for its excellent mechanical, electrical, thermal and optical properties. It can be produced by micro-mechanical exfoliation of highly ordered pyrolytic graphite, epitaxial growth, chemical vapor deposition, and the reduction of graphene oxide (GO). The first three methods can produce graphene with a relatively perfect structure and excellent properties, while in comparison, GO has two important characteristics: (1) it can be produced using inexpensive graphite as raw material by cost-effective chemical methods with a high yield, and (2) it is highly hydrophilic and can form stable aqueous colloids to facilitate the assembly of macroscopic structures by simple and cheap solution processes, both of which are important to the large-scale uses of graphene. A key topic in the research and applications of GO is the reduction, which partly restores the structure and properties of graphene. Different reduction processes result in different properties of reduced GO (rGO), which in turn affect the final performance of materials or devices composed of rGO. In this contribution, we review the state-of-art status of the reduction of GO on both techniques and mechanisms. The development in this field will speed the applications of graphene.     

Overpotentials and solid electrolyte interphase formation at porous graphite electrodes in mixed ethylene carbonate-propylene carbonate electrolyte systems

The first electrochemical lithium insertion was characterized for several graphite materials with high degree of crystallinity, different particle size distributions and surface morphologies in an ethylene carbonate (EC)/propylene carbonate (PC) electrolyte. For coarser graphite materials and graphites with a low superficial defect concentration, an irreversible process was observed which correlated with the electrochemical exfoliation of graphite. Different natural and synthetic graphites with similar particle size distribution and active surface area showed differences in the passivation behavior during the first electrochemical reduction. The fraction of graphite particles exfoliating during the first galvanostatic lithium insertion linearly increased with length of the irreversible plateau, which concomitantly moved to more positive potentials. This behavior can be rationalized when considering, besides the surface structure, local overpotentials for the solid electrolyte interphase formation process, and especially the overpotential distribution through the graphite electrode. These overpotentials cause a distribution of the local current density attributed to the passivation process. Optimizing the particle contacts in the electrode by applying mechanical pressure or by selecting the proper binder decreased the overpotentials and suppressed the graphite exfoliation in the EC/PC electrolyte. Therefore, both graphite surface structure and electrode engineering aspects have to be considered for successful passivation against exfoliation.     

高性能C/BN层状复合材料的研究进展

介绍了碳素石墨材料、六方氮化硼材料以及C/BN层状复合材料的主要性能和蒸镀工业中蒸发舟材料的发展状况;分析目前蒸镀行业中蒸发舟所能达到的水平及在使用过程中存在的一些问题;针对在制备C/BN层状复合材料中出现的问题,对今后需要展开的工作进行了简单的展望。     

Multilayered ceramic composites – a review

With the aim of improving the toughness of ceramic materials, laminated composites have been successfully developed since Clegg et al. (1990) inserted weak interfaces using very thin graphite layers between silicon carbide sheets and obtained a composite that exhibited non-catastrophic fracture characteristics. The weak interface must allow the crack to deviate either by deflection or delamination; in other words, the interface must exhibit a fracture resistance that is lower than that of the matrix layer. In parallel, ceramic laminated composites with strong interfaces were developed in which the residual tensile and compressive stresses appeared in alternate layers during cooling after sintering. These composites are prepared by stacking ceramic sheets produced by lamination or tape casting or by the sequential formation of layers by slip casting, centrifugation or electrophoretic deposition. The techniques may be combined to obtain a composite with the most adequate configuration. This work presents a review about the obtainment of multilayered ceramic composites as a toughening mechanism of ceramic plates.     

Effect of Interface Structure on Mechanical Properties of Advanced Composite Materials

This paper deals with the effect of interface structures on the mechanical properties of fiber reinforced composite materials. First, the background of research, development and applications on hybrid composite materials is introduced. Second, metal/polymer composite bonded structures are discussed. Then, the rationale is given for nanostructuring the interface in composite materials and structures by introducing nanoscale features such as nanopores and nanofibers. The effects of modifying matrices and nano-architecturing interfaces on the mechanical properties of nanocomposite materials are examined. A nonlinear damage model for characterizing the deformation behavior of polymeric nanocomposites is presented and the application of this model to carbon nanotube-reinforced and reactive graphite nanotube-reinforced epoxy composite materials is shown.     

Biomimetic Design of Artificial Materials Inspired by Iridescent Nacre Structure and Its Growth Mechanism

Nacre, the iridescent material found in the innermost layer of seashells, having high strength and toughness was obtained from relatively weak constituents. The excellent mechanical performance of this biological material originates from its hierarchically ordered arrangement of well-tailored hard and soft building blocks. Incorporating these structures into composites is as alluring as conventional engineering materials often sacrifice strength to improve toughness. The unique mechanical properties originated from multiscale deformation regime involving solid-state self-organization process lead efficient energy dissipation which leads to high toughness, these multiscale biological assemblies inspire new synthesis route of complex materials. In this review, we study various mechanisms involved in toughening, methods used in mimicking nacre structure and various strategies for fabricating nacreous architecture which has gleaned new avenues for self-standing, strong, and advanced toughened material.     

Effect of the core/shell latex particle interphase on the mechanical behavior of rubber-toughened poly(methyl methacrylate)

Two- and three-layer composite latex particles were used to prepare rubber-toughened poly(methyl methacrylate) (RT-PMMA). The interfacial thicknesses of the multi-layered particles were varied by using different emulsion polymerization synthesis techniques. The resulting interphases were previously characterized by ¹³C nuclear magnetic resonance techniques. The poly(divinyl benzene)/poly(butyl acrylate) (PDVB/PBA) interphase thickness was found to be in the range of 5–7 nm. It was also found that the PBA/PMMA interphase thickness could be varied from 5 to 7 nm (batch addition of MMA) to 15 to 17 nm (interphase compatibilized with PMMA macromonomer). The interphase thickness was expected to play an important role in the mechanical behavior of PMMA. The effect of the interphase of two- and three-layer particles on the tensile and fracture behavior of PMMA composites was evaluated. The fracture surfaces were examined by scanning electron microscopy. The two-layer PBA/PMMA particles with a thicker interphase (15–17 nm) exhibited higher K_IC values with the PMMA composites compared with PBA/PMMA particles with a thinner interphase (5–7 nm). The three-layer particles were found to be more effective in toughening PMMA compared with the two-layer particles. The differences in toughening behavior are speculated to arise from the morphological effects caused by a thicker interphase, which in turn results in better coverage by the PMMA shell and a more uniform distribution of the toughening particles in the PMMA matrix. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:581–593, 1997