The current high entropy alloys' studies are most in block, powder, coating, film and other areas. There are few studies of high entropy alloys in other areas and they are lack of unified classification. According to the current high entropy alloys' research situation, The paper has focused on the classification on all kinds of high entropy alloys having been researched, introduced the selecting principle of elements, summarized the preparation methods, reviewed the research institutions, research methods and research contents of high entropy alloys, prospected the application prospect of high entropy alloys, put forward a series of scientific problems of high entropy alloys, including less research on mechanism, incomplete performance research, unsystematic thermal stability study, preparation process parameters to be optimized, lightweight high entropy alloys' design, the expansion on the research field, etc, and the solutions have been given. Those have certain guiding significance for the expansion of the application of high entropy alloys subjects in the future research direction.

The properties of electronics, mechanics, magnetics and optics of nanometer materials were changed greatly because of their particular surface effect, volume effect and quantum size effect Nanotechnology was applied successfully to fine ceramics, microelectronics, bioengineering, chemical engineering and pharmacy fields.Its widely applied prospect made nanometer materials and corresponding nanotechnology become one of the hot topics in the scientific research field, which have great improvements on the materials'super-plasticity and high-strength, these characteristics have significant effects on the electronics, thermal dynamics, magnetics and optics of materials, they are regarded as another industrial revolution in the 21th century.

为确保直九国产化研制新材料不低于80年代法国标准先进水平,哈飞公司对新材料进行了系统的剖析.

Graphene-reinforced aluminum matrix nanocomposites were successfully synthesized through ball milling and powder metallurgy. The tensile strength and yield strength of graphene-reinforced aluminum matrix nanocomposites are remarkably enhanced by adding graphene nanoflakes(GNFs). Importantly, the ductility properties are remained excellently, which is firstly found in the second phase reinforced metal matrix nanocomposites. The microstructures were observed by OM, SEM and TEM method. And the tensile properties were tested.The results show that graphene nanoflakes are effectively dispersed and well consolidate with aluminum matrix, however, chemical reactions are not observed. The original structured characteristics of graphene nanoflakes are preserved very well. The average tensile strength and yield strength of nanocomposite are 454MPa and 322MPa, respectively,which are 25% and 58% higher than the pristine aluminum alloy at a nanofiller mass fraction of 0.3%, while the ductility increases slightly. The relevant mechanisms of strengthening and toughening enhancement are discussed on the base of 2D and wrinkled structured properties of graphene nanoflakes.

Thermal management systems, controlling the dispersion, storage and conversion of heat, were widely used in various fields of national economy and defence applications etc. Advanced thermal management materials form the material basis of the thermal management system, while the thermal conductivity was the critical property of all the thermal management materials. The application, classification, and physical mechanism of heat conduction of advanced thermal management materials were reviewed in this paper. The research progress and existing problems of thermal interface materials, high thermal conductivity packaging materials, thermal storage materials and thermoelectric materials were introduced. It is pointed out that molecular dynamics, density functional theory and large-scale parallel computing technology will play increasingly import roles in revealing the multi-scale heat transfer mechanism in the homogeneous and composite materials.

The recent progress on TEMPO-oxidized cellulose nanofibers(TOCNs) was reviewed. Research progress on fabrication of TOCNs was discussed, including development of TEMPO-mediated oxidation system, research on various of cellulose raw materials, and factor influencing the homogenization of TEMPO-oxidized cellulose. The latest application of TOCNs in composite materials, films, nanopapers and other fields was discussed. Furthermore, the development status was evaluated, the existing problems and developing trend of TOCNs were also introduced.

Since its invention and initial application in gas turbine components in the early 60’s of 20^th century at INCO Huntington Alloys (now called Special Metals Co.), INCONEL 718 alloy (IN718) has become the most widely used nickel based superalloy in the aircraft engine industry. It was used in many critical aircraft engine components, accounting for over 30% of the total finished component mass of a modern aircraft engine. This article reviews IN718 alloy development history, its mechanical properties, long-term thermal stabilities, industrial processing methods, and current developing substitute alloys for enhanced thermal stability.

The research progress and application status of ceramic 3D printing technology, and its materials characteristics were reviewed. The characteristics and research progress of inkjet printing technology, melt deposition molding technology, photocuring molding technology, layered entity manufacturing technology, laser selection melting technology/laser selective sintering technology, three-dimensional printing technology, and slurry write-through molding technology were discussed. The characteristics and application status of tricalcium phosphate ceramics, alumina ceramics, ceramic precursor, SiC ceramics, Si₃N₄ ceramics, and titanium silicon carbide ceramics were analyzed. It was pointed out that the development direction of ceramic 3D printing technology is combined with traditional ceramic technology to realize the rapid production of ceramic products and the manufacture of bio-ceramic products and high-performance ceramic functional parts.

Some advanced high temperature titanium alloys are usually selected to be manufactured into blade, disc, case, blisk and bling under high temperature environment in compressor and turbine system of a new generation high thrust-mass ratio aero-engine. The latest research progress of 600℃high temperature titanium alloy, fireproof titanium alloy, TiAl alloy, continuous SiC fiber reinforced titanium matrix composite and their application technology in recent years in China were reviewed in this paper. The key technologies need to be broken through in design, processing and application of new material and component are put forward, including industrial ingot composition of high purified and homogeneous control technology, preparation technology of the large size bar and special forgings, machining technology of blisk and bling parts, material property evaluation and application design technique. The future with the continuous application of advanced high temperature titanium alloys, will be a strong impetus to the development of China's aero-engine technology.

The research status on theoretic models and the coupling relationships of Orowan strengthening, dislocation strengthening, load-bearing effect of the reinforcement strengthening and others strengthening are successfully described in this study for particle-reinforced metal matrix composites(MMCs) with a volume fraction lower than 14%. Some conclusions can be obtained:Orowan strengthening and dislocation strengthening stress can be enhanced by increasing volume fraction, decreasing size of reinforcement and improving homogeneous distribution of reinforcement, load-bearing strengthening stress can also be enhanced by increasing volume fraction; yield strength and ductibility of MMCs can be enhanced much more by increasing load-bearing strengthening stress and plastic deformation region and adopting the material design method of metal matrix surrounded by particles with microstructural inhomogenous distribution; grain boundary strengthening and Peierls-Nabarro stress can also affect the yield strength of MMCs as a part of matrix strengthening, solid solution strengthening can be ignored usually; there are three coupling relationships for the sum strengthening contributions:linear summation, multiplicative combination and the root of the sum of the squares. The linear summation and multiplicative combination can be applied to nanoparticle-reinforced MMCs, the linear summation is generally applicable in the case when there are few factors influencing the strength, the multiplicative combination is the most commonly used method. The root of the sum of the squares is applied to micronparticle-reinforced MMCs.

After introducing the principle and classification of 3D printing, methods for metal forming using 3D printing were reviewed in details, including electron beam melting(EBM), selective laser melting(SLM), laser direct melting deposition(LDMD). The application fields of metal 3D printing and research status overseas and domestic were also discussed in this paper. At last, based on the current development of metal 3D printing, this paper summarized the key issues that should be solved, which include the quality of powders, the usage of 3D printing equipments, nondestructive testing for 3D printing components, the failure analysis and prediction of lifecycles for 3D printing components. The standards of nondestructive testing for 3D printing components should be established and the database of comprehensive mechanical properties for 3D printing materials should be built.

High-entropy alloys were newly developed alloys that were composed,by definition,of at least five principal elements with concentration in the range of 5%-35%(molar fraction).Therefore,the alloying behavior of any given principal element was significantly affected by all the other principal elements presented.The definition,distinguished structure and performance characteristics,as well as the potential applications of high-entropy alloys were introduced.In addition,the historical development and the latest research progress in this field are also summarized.

The present status of research and application about the aircraft brake disk and the engine hot components manufactured by carbon/carbon (C/C) composites in the world has been introduced in the paper.The problems in the studying works and the development directions about this field on the future have been discussed.

Graphene oxide (GO) has wide applications and development prospects in the functional composites owing to its many unique properties, such as two-dimensional structure and large theoretical specific surface areas as well as hydrophilic and polarized interface. The present situation and progress of the graphene oxide composites used in reinforcing and toughening, adsorption separation, photocatalysis and biological medicine were introduced in this paper. The mechanism of producing reinforcing and toughening of polymer and cement based composites caused by forming regular and ordered microstructure regulated with GO nanosheets was mainly summerized. Meanwhile, application principle of the GO composites in the field of adsorption, photocatalysis and biological medicine were analyzed. Finally, the application and development trend of GO composites in reinforcing and toughness as well as adsorption and photocatalysis were pointed out.

With the increase of the thrust-weight ratio of the aero-engine, CMC-SiC composites with low density, high strength and toughness, high thermal stability, long lifetime, good ablation resistance and oxidation resistance need to be developed to meet the requirements of the complicated and aggressive environments in the aero-engine. The characteristics, fabrication methods, applications on the hot components of the abroad advanced aero-engines, the domestic research achievements and the open problems of the CMC-SiC composites were introduced. The research tendencies in the high performance fibers, parts design and fabrication, environmental barrier coatings, non-destructive testing technologies, evaluation and verification method and repairing technologies were put forward.

Electromagnetic response of metamaterials is not only determined by its component materials but also the microstructure and arrangements of its resonant elements. The perfect absorber prepared by metamaterial (PMA) can realize 100% absorption in specific frequency bands by designing reasonable structures of resonators. PMA can be applied in many domains, such as stealth material, frequency selective surface, terahertz imaging, micro antenna, intelligent communication, detection and regulation of electromagnetic wave because of its flexible designing, adjustable response, strong absorption, broad band, thin thickness, light mass. Based on the present study situation at home and abroad, we summarized the development, structure, preparation and test of PMA. In order to gain a more profound and comprehensive understanding on PMA, we also explored its trends, prospects and urgent problems. Proactive and intelligent PMA with multi functions and new PMA prepared by new material and new process are the future development trends.

Graphene was prepared by the classic Hummers method. By changing reaction temperature, reaction time, oxidant addition and reductant addition, the key processes that influenced the preparation were studied. The result shows that keeping the high temperature stage in the range of 90-100℃ is the most important factor to ensure high yield. In order to improve yield, the low and intermediate temperature stages should be kept close to 0℃ and 30-45℃, and the reaction time should be longer than 30min and 60min respectively. Moreover, excess oxidants is also an important factor.

The development status of micro-arc oxidation (MAO) technology at home and abroad was reviewed. The principle and process characteristics of MAO technology were primarily introduced. The influence factors for the microstructure and properties of MAO ceramic coatings as well as the applications of MAO technology were summarized. Also, the existing problems of MAO technology were analyzed, and it has been pointed out that MAO technology will be developed towards the direction of low energy consumption, treatment of ultra-large and complex light metal components and combining with other surface technologies in the future.

Intelligent material is a new type of smart multifunctional material that can spontaneously sense the change of external environment and judge, handle and properly make the response. At the same time, it's also the fourth generation material after natural material, synthetic polymer and artificial design material, triggering a new revolution in material science. Starting from the historical origin of shape memory composite, this paper details the latest development of shape memory alloy and shape memory polymer from aspects of shape memory mechanism and engineering application. The discussions of recent technological problems are also included, such as the weak biocompatibility, small deformation, slow actuation velocity and brief fatigue life of SMA as well as the complex manufacture of 3D printing, small strength and stiffness of SMP, etc. The possible near development directions are finally forecasted.

Perovskite solar cells(PSCs) have been developed rapidly as one of the most remarkably growing photovoltaic technologies in the last five years. The power conversion efficiency(PCE) of the solar cells has been unprecedentedly increased over the relatively short period. It is of great significance to study the perovskite materials in this kind of solar cells for improving the efficiency. The most focused issues as well as the main progress in varied fabrication techniques and synthesis of new materials in recent years were reviewed in this paper. The characteristics and improvements of varied fabrication techniques are introduced in detail, the necessity and the problems facing for new materials synthesis were analyzed. Finally, a perspective view on reducing the toxicity of perovskite, preparing large-scale perovskite solar cells, and the cost reduction was given to provide the direction for the future research of high-efficiency and stable perovskite solar cells.

Graphene is a single atomic layer structure, which is the thinnest 2-D planar sheet composed of sp²-bonded carbon atoms. The special structure of graphene has excellent properties, such as photoelectric property, heat stability and mechanical properties. There has been increasing attention to preparation, property and application of graphene composites in recent years. In the paper, preparation methods of graphene composites is reviewed, such as graphene/polymer composites, graphene/metal (metal oxide) composites, and ternary composites of graphene. The advances in application of graphene composites are also reviewed, such as in lithium battery, supercapacitors, photovoltaic devices, sensor applications. Furthermore, the important research direction of graphene composites is pointed out.

As a new type of two-dimensional nanomaterials, MXene has been widely investigated since its discovery at 2011 due to its excellent physical and chemical properties, such as high conductivity, good lubricity, electromagnetism and other special properties. Hence, in addition to the performance of the traditional two-dimensional materials, MXene has been extensively used in the fields of energy storage, catalysis, lubrication, electromagnetic shielding, sensor, water purification and so on, and certain results and progress were achieved. The latest researches of MXene at structure, property and preparation methods, as well as the related achievements in lithium ion battery, supercapacitor and others at our country and overseas in recent years were reviewed in this paper. Moreover, the shortcomings of current research were summarized, and the future research direction were prospected as well.

The energy crisis and environmental pollution problem is increasingly serious on a global scale, however the rapid development of photocatalytic technology brings the dawn to solve the problem, and the photocatalytic materials system as a basic element has become the focus. The photocatalytic degradation of organic pollutants in water was focused in this article, and the development status of photocatalytic technology, nine types of photocatalytic materials and their properties, mechanism of action and the application of research, as well as modification methods of the materials were summarized. Finally, it was proposed that the materials still has the problems of low solar energy utilization, low quantum yield, and insufficient photochemical stability at the current stage, nevertheless the new material system of metal-organic framework (MOF) and the modification methods of micro/nano mesoporous, multi-hole composite, Z-scheme semiconductors provide a broader space for the exploration of photocatalytic materials.

Based on the brief review of accelerated developing status of aircraft power technology in the world, the present status and developing trend of key materials technology for aero-engine were analyzed. In accordance with the idea of "one generation of new material, one generation of new type engine", development requirements for the materials technology of the system and main parts of aero-engine were proposed. Suggestions for improving development and application level of the materials technology in China were presented from aspects of quality stability and technical maturity, investigation and verification for engineering, materials system and data, composite materials, airworthiness certificate, etc.

Currently, the utilization efficiency of energy still remains at a low level, although the depletion of fossil fuel is appoaching. Therefore, it is of great significance to develop new materials and technologies for energy-saving and environment protection. Phase-change materials (PCM), which can absorb or release heat through inversible phase change, are very promising in the fields of heat storage and thermal management. In this paper, the characteristics and classification of PCM were introduced briefly in the first section, and then the application and development status of PCM were reviewed and analyzed detailedly. In the third part, the main problems of PCM were pointed out, and the related research work and recent research progress were analyzed and discussed. Finally, it was pointed out that optimizing material properties through new functional composite technology, designing new material system, expanding new application fields are the main development directions of phase change energy storage materials.

The properties of cathode materials play an important role in the development and application for lithium ion batteries. However, their phase transition, low conductivity and side reaction with electrolyte restrict the further improvement of battery performance. Coating is one of the effective techniques to overcome these problems. This paper focuses on the influence of surface coating on the properties of cathode materials for lithium ion batteries. The research progress of various coating materials was summarized. The modification mechanism of coating materials was also elaborated. And the future development trend of coating materials was proposed, for example, exploring continuously new coating materials with excellent performance, investigating in depth coating mechanism, and optimizing further coating technologies.

Membrane electrode assembly (MEA) is the core component of proton exchange membrane fuel cell (PEMFC), which provides the microchannels for the transfer of multiphase substances and electrochemical reaction sites. To achieve the commercialization of PEMFC, fabricating MEA with high power density, low Pt loading and good durability is needed. Inside MEA, the structures of function layers and the interfaces between layer to layer all have great impact on the performance of MEA outside of the catalyst. The MEA prepared by traditional methods (CCS method and CCM method) has many structural defects, which greatly reduces the utilization rate of Pt and the mass transfer ability. By optimizing the structure of each functional layer to eliminate defects, it will be beneficial to further improve the comprehensive performance of PEMFC. Based on the problems existing in the traditional MEA structure, literatures in recent years on the improvement of the structure of CL, PEM and GDL were combed, and the preparation methods, structure-activity relations, and advantages/disadvantages of each advanced structure were summarized. This paper will provide a guidance for the development of MEA with high performance, low cost and long service life in the future.

The research of SiC_f/SiC ceramic matrix composites (CMCs) as well as their applications in aero engines has obtained rapid development recently. This is owing to the large quantity of coupon tests performed on various properties of these materials, and the establishment of corresponding databases. Here, the physical and mechanical properties of CMCs developed by SNECMA, NASA and GE were reviewed. The influence of fabrication techniques on the properties of materials were discussed with an emphasis on tensile properties. Meanwhile, the service performances of these materials were summarized, including oxidation, water vapor/oxygen environmental resistance at high temperature, fatigue and creep behaviors, resistance to thermal shock and foreign object damage, along with the mechanism of damage and failure in environments such as heating, loading, water and oxidation. At last, some suggestions about domestic further research on performances testing for SiC_f/SiC ceramic matrix composites were proposed.

Metamaterials, man-made materials, enable us to design our own "atoms", and thereby to create materials with unprecedented effective properties that have not yet been found in nature. Smart metamaterial is one of those that is an intelligent perceptive to the changes from external environments and simultaneously having the capability to respond to thermal and mechanical stimuli. This paper can provide a review on these smart metamaterials in perspective of science, engineering and industrial products. We divide smart metamaterials according to what they are tuning into: optical, mechanical, thermal and coupled smart metamaterials. The rest of two techniques we addressed are modelling/simulation and fabrication/gene engineering. All of these types smart materials presented here are associated with at least five fundamental research: coupled mechanism of multi-physics fields, man-made design for atom/molecular, metamaterials coupled with natural materials, tunability of metamaterials, and mechanism of sensing metamaterials. Therefore, we give a systematic overview of various potential smart metamaterials together with the upcoming challenges in the intriguing and promising research field.

Graphene, a two-dimensional carbon material made up of a single atomic layer structure, shows unique physical and chemical properties.Graphene reinforced metal matrix composites have attracted more and more attention due to excellent properties.In this paper, the synthesis methods of graphene reinforced metal matrix composites were reviewed.The research progress of graphene reinforced metal matrix composites in strength, thermal conduction, conductivity and corrosion resistance was comprehensively analyzed.Finally, on the basis of pointing out the importance of the study on interfacial bonding mechanism, the development trend of graphene reinforced metal matrix composites in improving the performance and extending the scope of application was prospected.

The latest research progresses on Fe-based amorphous coatings were reviewed. The typical alloy system and the classification of Fe-based amorphous coatings were clarified. The status, progress and development of the Fe-based amorphous coatings prepared by thermal spray processing and laser cladding process were discussed. The main mechanical properties and potential applications of the Fe-based amorphous coatings were also described. Furthermore, based on the main problems mentioned above, the future development of the Fe-based amorphous coatings was discussed, including the exploitation preparation technologies of high amorphous content of the Fe-based coatings, the development of the low cost and high performance Fe-based coating alloys system, the broadening application of Fe-based amorphous coatings, and so on.

Casting defects are deleterious to the mechanical properties of nickelbased single superalloys, the decrease of casting defects is benefit for improving mechanical properties and reducing the cost. Some important casting defects formed in the directional solidification process are discussed, including porosity, freckles, misorientation and stray grains. Based on the features and formation mechanisms for the defects, the influence of alloy composition, processing parameters and casting structure on the casting defects is analyzed. Meanwhile, the suggestions for reducing casting defects are pointed out.

The basic principles and methods of infrared radiation and infrared stealth technology were discussed in this paper. It was found that flexible regulation of multi-band spectrum was the key to realize infrared stealth compatible with radar stealth, laser stealth and visible light stealth. The research status of traditional infrared stealth materials were summarized and the bottleneck of their development was clarified. Furthermore, the design idea, research basis and development advantages of infrared stealth metamaterials with spectral tailoring function were proposed. We reviewed the research status and development trend of the infrared stealth compatible with radar stealth, infrared stealth with infrared radiation window and infrared stealth compatible with laser and visible light.

The main problems in high-dielectric-constant polymer composites are reviewed. The composites of polymers with ceramics, conductive particles (metal particles, graphite and carbon nanotubes) are summarized. The review also narrates copper phthalocyanine and polyaniline modified all-organic high-K composites. Meanwhile, problems facing the traditional high-K polymer composites are discussed. At last, the prospects of the possible developments in the future are proposed, that is to enhance the dielectric constant, energy density, and to decrease the dielectric loss and production cost.

Polymer hydrogel is a soft material with a three-dimensional network structure that can absorb and retain a large amount of water. Polymer hydrogels have good biocompatibility, mechanical properties and important application value in biomedical and bioengineering fields. Self-healing hydrogels are smart hydrogels that respond to external stimuli and repair their own damage. Compared with the traditional hydrogel, the self-healing hydrogel has the property of repairing damage, and received extensive attention in the scientific field in recent years. Dynamic chemistry-based self-healing hydrogels are novel self-healing hydrogels that can reshape three-dimensional network structures by dynamic covalent or non-covalent bonding to repair damage. The new self-healing hydrogel can quickly repair its own damage and has good environmental adaptability, laying the foundation for the development of self-healing hydrogels as multifunctional new materials. The research progress of recent self-healing hydrogels based on dynamic chemistry was reviewed in this paper, especially focusing on the updated development on self-healing hydrogels based on hydrogen bonds, metal coordination interactions, host-guest interactions, ionic bonds, hydrophobic interactions, imine bonds/acylhydrazone bonds, borate bonds and disulphide bonds, and meanwhile, the problem of self-healing hydrogels was put forward, and the future direction of development was finally predicted.

A novel method to fabricate flexible free-standing electrodes with textile structure for lithium-ion batteries was provided by applying extrusion-based three-dimensional (3D) printing technology. Meanwhile, highly concentrated poly(vinylidene fluoride) (PVDF) is used as viscosity modifier, carbon nanotube (CNT) as conducting additive, and lithium iron phosphate (LFP) or lithium titanium oxide (LTO) as cathode or anode active materials respectively to develop printable inks with obvious shear-thinning behavior, and with the apparent viscosity and storage modulus platform value of over 10⁵Pa·s, which is beneficial to the printability and enable complex 3D structures solidification. The electrochemical test shows that both printed electrodes have similar charge and discharge specific capacities under current density of 50mA·g^-1. To explore the feasibility of the printed electrodes, a pouch cell with as-printed LFP and LTO electrode as cathode and anode respectively is assembled. The pouch cell without deformation delivers discharge specific capacities of approximately 108mAh·g^-1, and there is a tiny increase in discharge specific capacities of around 111mAh·g^-1 for bended pouch cell.

The preparation methods, luminescence mechanism and application research progress of carbon dots (CDs) were summarized. Approaches for synthesizing CDs were emphasized, and can be generally classified into two main ways: bottom-up and top-down methods. Top-down methods include arc discharge, laser ablation and electrochemical oxidation methods and others, and bottom-up approaches consist of combustion routes, template synthesis methods, hydrothermal methods, thermal methods and others. The advantages and disadvantages of these methods and fluorescent quantum yield were evaluated, and the research trend of these methods was prospected. It is pointed out that the synthetic/modified methods of CDs and the luminescence mechanism need to be further studied to improve the quantum yield in the future research, and it is crucial to synthetic CDs with the fluorescent which can be precisely, sensitively, rapidly and easily detected in the application of CDs as a new technique and a new method in all kinds of chemical detections and analysis.

Shape memory polymers(SMPs) are a class of functional "smart" materials that have shown bright prospects in the area of biomedical applications. The novel smart materials with multifunction of biodegradability and biocompatibility can be designed based on their general principle, composition and structure. In this review, the latest process of three typical biodegradable SMPs(poly(lactide acide), poly(ε-caprolactone), polyurethane) was summarized. These three SMPs were classified in different structures and discussed, and shape-memory mechanism, recovery rate and fixed rate, response speed was analysed in detail, also, some biomedical applications were presented. Finally, the future development and applications of SMPs are prospected: two-way SMPs and body temperature induced SMPs will be the focus attension by researchers.

Wire and arc additive manufacturing (WAAM) was investigated by tungsten inert gas arc welding method (TIG), in which φ1.2mm filler wire of aluminum alloy 5A06(Al-6Mg-Mn-Si) was selected as deposition metal. The prototyping process was conducted by a TIG power source (working in AC mode) manipulated by a four-axis linkage CNC machine. Backplate preheating temperature and arc current on deposited morphologies of single layer and multi-layer were researched. The microstructure was observed and the sample tensile strength was tested. For single layer, a criterion that describes the correlation between backplate preheating temperature and arc peak current, of which both contribute to the smoothening of the deposited layer. The results show that the layer height drops sharply from the first layer of 3.4mm and keeps at 1.7mm after the 8th layer. Fine dendrite grain and equiaxed grain are found inside a layer and coarsest columnar dendrite structure at layer boundary zone; whereas the microstructure of top region of the deposited sample changes from fine dendrite grain to equiaxed grain that turns to be the finest structure. Mechanical property of the deposited sample is isotropic, in which the tensile strength is approximately 295MPa with the elongation around 36%.

SiC matrix ceramic composites (CMC-SiC) are considered as the potential primary structural materials in advanced gas turbines because of their low density, good oxidation resistance and high-temperature strength. However, CMC-SiC suffers from serious degradation in the gas environments. With the protection of environmental barrier coatings (EBCs), CMC-SiC composites can be possibly applied as hot components with long lifetime in the aero-engine. The materials selection requirements, development history, preparation process, assessment technologies and characterization methods of EBCs materials system were introduced in this paper. The open problems of EBCs materials system such as high volatile rate, low operating temperature during service and low crystalline fraction, low density of the coatings during the preparation process were summarized and analyzed. The research goal and development direction in the EBCs system optimization, fabrication process development and evaluation and assessment platform were put forward.