Progress of Materials Science in Space Technology in China (2020–2022)*

WEI Qiang LIU Yue XIA Chaoqun

1(Key Laboratory of Hebei Province on Scale-span Intelligent Equipment Technology, School of Materials Mechanical Engineering, Hebei University of Technology, Tianjin, 300401)

2(State Key Laboratory of Reliability and Intelligence Electrical Equipment,Hebei University of Technology, Tianjin, 300401)

3(School of Materials Science and Engineering, Hebei University of Technology, Tianjin, 300130)

Abstract In this paper,the main research work and related reports of materials science research in China’s space technology field during 2020–2022 are summarized.This paper covers Materials Sciences in Space Environment,Materials Sciences for Space Environment,Materials Behavior in Space Environment and Space experimental hardware for material investigation.With the rapid development of China’s space industry,more scientists will be involved in materials science,space technology and earth science researches.In the future,a series of disciplines such as space science,machinery,artificial intelligence,digital twin and big data will be further integrated with materials science,and space materials will also usher in new development opportunities.

Key words Materials sciences in space environment,Materials sciences for space environment,Materials behavior in space environment,Space experimental hardware for material investigation

1 Introduction

The integration of space technology and material science has formed a series of new disciplines with space environment as the intersection point.As a new interdisciplinary field,space materials science describes the relation between space environment and materials.On the one hand,space environment effects on materials are harsh to spacecraft and its materials,such as charged particle radiation and atomic oxygen[1–3].Under the space environment the research and protection of damage mechanism and performance evolution of materials is necessary.On the other hand,space environment is special environment,such as weightlessness,and novel materials can be prepared in the special environment[4,5].

Generally speaking,space material science is the science of studying the structure and properties of materials and the laws of the preparation process,as well as the physical and chemical properties of materials and their working behavior under the space environment conditions such as microgravity,space radiation and high vacuum[6,7].Aerospace materials science is the study of the design,preparation,properties and adaptability of materials used in spacecraft.In recent years,the on-orbit manufacturing of spacecraft materials in the space station has been realized[8,9].At the same time,ground simulators are becoming more and more perfect.Space environment,as an extreme environment,can be more effectively reproduced.Material structure,properties,preparation and service behavior can be further studied on the ground.With space environment as the link,space materials and aerospace materials are further integrated to form three research directions,as shown inFig.1.These research directions are as follows.

Fig.1 Cross fusion of materials science in space technology

(1) Materials Sciences in Space Environment:study on physical and chemical properties,phase transformation process,synthesis and forming principle of new materials under space environment.

(2) Materials Sciences for Space Environment:research on design,manufacture,processing and production technology and principle of space materials for service and development in space environment.

(3) Materials Behavior in Space Environment:Study on the behavior and adaptability of various materials in service under space environment.

Based on literature retrieval and online public information,this paper focuses on the reports in China’s space and space materials field from 2020 to 2022,and summarizes relevant Chinese scholars’ literature and reports to reflect the progress of materials science in China’s space technology field in recent years.

2 Materials Sciences in Space Environment

2.1 Development Strategy Album on Space Materials

Space materials science has gone through half a century since its birth in 1969 and its subsequent development until 2019.In 2019,The National Natural Science Foundation of China and the Chinese Academy of Sciences jointly released the “ China Discipline Development Strategy—Space Science”,and space material science has become one of the space science fields supported by the development of China’s manned space station and Space Science Pilot project.The development strategy outlines the development of China’s space materials science in the next 10 years and up to 2050.Under the guidance of the development strategy of space science,it was reported that some research results of materials and components manufacturing experiments and applications carried out by Chinese scientists on the Shijian-10 microgravity science satellite,Tiangong-2 space flight platform in recent years.At the same time,some basic and applied research results and future research trends of materials science in space microgravity,which cannot be simulated on the ground,are introduced[6].

2.2 Recent Achievements in Space Materials Research

Prof.Bingbo Wei and his team from Northwestern Polytechnical University have been conducting research on space materials for many years and have achieved fruitful results.In 2020,the team summarized the main progress in the study of four aspects from home and abroad in the recent 20 years,including space environment physical and chemical characteristics,space liquid nature of the material under the condition of forming process of kinematics and kinetics of phase transformation,space materials preparation,as well as microstructure and properties of material in space environment regulation,and the future development trend of this field is further analyzed and forecasted[7].

In 2020–2022,the team also achieved new results in ground simulation of microgravity and containerless preparation and characterization of Mo-Ni and Ni-Ge alloys.

2.2.1 Mo-Ni alloy under Containerless Microgravity Condition[10]

The microgravity rapid solidification and microstructure control of Mo-48%Ni alloy with droplet diameter from 144 μm to 1530 μm was achieved by free-fall technique to simulate space environment conditions.The results show that the rapid solidification microstructure was composed of primary NiMo dendrites and (Ni+NiMo)eutectic,and the rapid cooling condition inhibited the subsequent solid phase transition.With the increase of droplet cooling rate and subcooling degree,the coarse NiMo dendrites were gradually refined,and the solute Ni content first decreased and then increased.The eutectic morphology changes from regular lamellar to irregular structure,in which the content of solute Mo increased first and then decreased.The elastic modulus of primary phase and eutectic structure decreased monotonically.The microhardness of primary phase increased slowly at first and then decreased,and the microhardness of eutectic microstructure decreased as a whole.At the same time,the magnetization of the alloy decreased,but the coercivity and the temperature resistance were improved.

2.2.2 Ni-Ge Alloys under Simulated Microgravity Condition

The rapid solidification of Ni95Ge5 single-phase alloy and Ni33Ge67 eutectic alloy was achieved by means of drop-tube containerless processing and copper-mold injection casting.The microstructure evolution,hardening mechanism and multi-scale mechanical properties of Ni95Ge5 and Ni33Ge67 eutectic alloy were systematically studied.It is found that with the increase of melt cooling rate,the microstructure of Ni95Ge5 single-phase alloy changes from coarse dendritic structure to equiaxed grains structure,while Ni33Ge67 eutectic alloy gradually changes from regular eutectic to hypereutectic with a few primary Ge phases.The hardening behavior of the single-phase alloy is grain boundary dominated,while that of the eutectic alloy is multi-phase co-hardening.Nanomechanics analysis shows that the eutectic alloy has higher surface stress and higher elastic recovery during unloading.While,single-phase alloy is more prone to plastic deformation.The special morphology evolution and lower strain hardening exponent of Ni95Ge5 alloy remarkably improved the hardening ability.Its hardness increased up to 56.6%,which was much higher than the eutectic alloy.The average ratio of microhardness to yield strength of single-phase alloy is 2.75,while that of eutectic alloy is 9.09.Therefore,the microstructure evolution caused by high cooling rate can also improve the yield strength of alloy materials.Due to the higher cooling rate of the droplet in the falling tube,the hardness and strength of the alloy after rapid solidification are significantly better than those of the spray casting alloy[11].

2.3 Research on Space Additive Manufacturing Process

In February 2016,the Center for Space Application Engineering and Technology of the Chinese Academy of Sciences carried out experiments on space additive manufacturing technology,carrying out 93 parabolic flight tests in three sorties in Bordeaux,France.In this experiment,five kinds of materials and two kinds of manufacturing processes were verified in microgravity test,and the data of different materials and processes in microgravity environment were obtained.In the experiment,the equipment and process independently developed by China were used to not only print the target sample,but also observe the influence of microgravity environment on the manufacturing process and materials,and collect a lot of important data[12].

In addition to flight tests,some Chinese scholars have also carried out experimental research on the ground forming process of different materials in order to solve the space application problems of FDM technology.Three pure resin materials including Polylactic Acid(PLA),Polycarbonate (PC) and Polyether Ether Ketone(PEEK) as well as carbon fiber reinforced PLA materials were selected as the research objects.The standard sample was successfully printed using the self-developed space microgravity principle prototype.The mechanical properties,flame retardant properties,gas concentration after combustion,mass loss,volatilization and other data were tested.The performance differences of PLA,PC,PEEK material FDM forming parts and traditional injection parts were compared and analyzed,as well as the tensile properties of carbon fiber PLA composite samples with different fiber directions[13].Results showed that binding strength between different materials is the main factor affecting the performance of FDM molding parts.The stronger the binding ability,the higher the quality of FDM forming materials.The forming quality of crystal materials is also affected by crystallinity,the higher the crystallinity,the better the performance of parts.

On 7 May 2020,China successfully launched its new generation of manned spacecraft aboard a Long March-5B carrier rocket.A “3D printer” on board the test spacecraft carried out China’s first additive manufacturing experiment in space.There are two objects printed in this experiment.One of them is the honeycomb structure (representing the lightweight structure of the spacecraft),and the other is the CASC logo (China Aerospace Science and Technology Corporation Limited).Continuous fiber-reinforced composites are the main materials for spacecraft structures at home and abroad because of their low density and high strength.Research on 3D printing technology of composite materials in space is of great significance for long-term in-orbit operation of future space stations and in-orbit manufacturing of super-large space structures[14].For example,the technology could enable on-orbit manufacturing on demand to support long-term manned operations and maintenance of space stations in orbit.It will also make it possible for China to expand its space station in orbit.

3 Materials Sciences for Space Environment

Aerospace material engineering involves many aspects of space environment and material science including space environment and effect analysis of aerospace materials,adaptability evaluation of space environment for aerospace materials,flight test technology of aerospace materials,space material science experiment with space material as research object,aerospace material guarantee related to the selection of aerospace materials and the development of new aerospace materials,and so on.With the longer and longer in-orbit operation time of spacecraft,the achievements of space materials science have gradually become the way to develop new materials for spacecraft,so there are more and more studies on the cross fusion of space materials and space materials.

3.1 Metal Materials

In recent years,the research group of Professor Riping Liu from Yanshan University has cooperated with The General Design Department of Beijing Space Aircraft,Baoji Titanium Industry Co.,Ltd.,and Western Metal Materials Co.,Ltd.,in the research and development,application and promotion of new TiZr-based alloys(Ti-Zr,Ti-Zr-Al,Ti-Zr-Al-V,Ti-Zr-Al-V-O,etc.)[15–18].Smelting and forging processes were established,and a series of new types of high strength and toughness TiZrbased alloys were prepared.The new TiZr-based alloys were successfully applied to space-critical components.

Based on metal matrix composites,the team of Professor Lin Geng of Harbin Institute of Technology has carried out the design and verification of two-dimensional layered structure of metal matrix composites and three-dimensional network structure of titanium matrix composites[19–21].By adjusting the content,size and distribution of component phase,the optimal configuration of mechanical properties of metal matrix composites can be achieved.The inversion relationship between strength and plasticity (toughness) of metal matrix composites was solved by the design of component phase structure.Huanget al.from Harbin Institute of Technology significantly improved the plasticity and strength of Titanium Matrix Composites (TMC) manufactured by Powder Metallurgy (PM) by designing the reinforcement distribution of a novel network structure.The design concept of Ti5Si3 +TiBw/Ti6Al4V composite was proposed based on Hashin-Shtrikma grain boundary theory[22].Zhanget al.[23]from Southeast University prepared Ti6Al4V (TC4) based nanocomposites with 3D network structure by SPS,which had excellent mechanical properties and ductility,and realized the network distribution of nanodiamond (ND) reinforced materials in TMC,effectively resolving the conflict between strength and ductility of TMC.

A high-performance silicon carbide particle reinforced aluminum matrix composite (SiC/Al) developed by the team of Ma from Shi Changxu Advanced Materials Innovation Center of Shenyang Institute of Metal Materials,Chinese Academy of Sciences,has been applied to the key components of solar wing extension mechanism and the core module of Tianhe in China Space Station[24,25].The team broke through the batch preparation technology of powder metallurgy and the plastic forming technology of isotropic medium thick plate.The production efficiency of billet was increased by more than 5 times,the finished product rate of plate was increased by 20%,and the performance difference between product batches was less than 5%.The magnesium alloy surface treatment technology developed by the team of Han and Song from the Material Corrosion and Protection Center of the Institute of Metals has been applied to the medical sample analysis of the core cabin and the high microgravity scientific experiment cabinet(short for high microgravity cabinet),the main structural subsystem of containerless scientific materials laboratory cabinet,and magnesium components used in automatic locking release mechanism of high micro cabinet suspension test system.It meets the multifunctional requirements of weight reduction,corrosion resistance and electric conductivity[25].

3.2 Inorganic Nonmetallic Materials

Shaoming Dong,Director of Shanghai Institute of Ceramics,Chinese Academy of Sciences,invented ceramic matrix composites with high structural stability.In the case of temperature change and stress in space environment,the deformation is close to zero,which creates a new system of supporting structure materials for space camera in China.The innovation called a “ stationary bracket” for a camera,has helped China’s satellite reach the Yami level (Gaofen-2) for the first time.The team established the preparation technology of ceramic matrix composites based on in-situ reaction,realizing the low-cost preparation and engineering of high-performance (ultra) high-temperature ceramic matrix composites that can withstand high temperatures up to 2000℃for new high-speed aircraft[26,27].The integral structural design concept of components is developed,and the technical route of large complex structure ceramic matrix composite integral components is opened,which greatly improves the application reliability of components[28].

Jixin Chen,associate researcher of Shenyang National Research Center for Materials Science,Institute of Metal Research,led the team to solve the problems of boron nitride ceramic materials,such as low strength,easy moisture absorption,unstable cavity discharge state,poor ion sputtering resistance[25].The boron nitride composite has the advantages of low density,high strength,thermal shock resistance,sputtering resistance,easy machining and good insulation performance,and is applied to hall thruster cavity in the core cabin electric propulsion system.

In view of the problem of maintaining the thermal balance in sealed capsule spacecraft under the extreme conditions of manned lunar landing,round-trip and round-trip flight around the moon,Pinget al.[29]proposed a thermal control coating material system with low absorption and low emissivity,which is suitable for space and ground environment.The material system used aluminum powder and silicone resin as the main raw materials.The Bruggeman model effective medium theory and Fresnel formula were used to calculate the variation between the volume fraction and the reflectance of the coating.Thermal controlled coatings with different ratios were prepared and their thermal radiation properties were tested.The results show that solar absorption ratioαSand hemispheric emissivityεHof low absorption-low emissivity thermal control coating are 0.15 and 0.15,respectively.The higher the proportion of aluminum powder filler is,the lower the thermal radiation performance of the coating is,which accords with the simulation conclusion between the volume fraction and the reflectance of the coating.

Spacecraft materials produce organic small molecule coagulable volatiles in space environment.These organic molecules condense on sensitive surfaces such as optical lenses and solar cells,which will greatly affect the safety and reliability of spacecraft.The active control of pollutants by adsorbent materials is one of the effective methods to solve space molecular pollution.Zeolite material with uniform pore size distribution and excellent adsorption performance is one of the ideal materials for the adsorption of spatial molecular pollutants.Panet al.[30]from Tianjin University prepared a monolithic adsorption material with 13 X-sic adsorption coating by microwave sintering technology using cordierite as the substrate.Zhanget al.prepared zeolite@TiO2composite material with high adsorption performance by designing modified zeolite material.Gonget al.[31]prepared Al2O3@5 A zeolite molecular sieve composites by Atomic Layer Deposition (ALD).These results provide theoretical and technical basis for material selection and application of adsorption materials for space molecular pollutants[32].

4 Materials Behavior in Space Environment

The interaction between space environment and matter is a key research field of space materials.The science of interaction between space environment and matter not only reveals the basic laws of the evolution of matter structure under the action of space environment supporting for reliable,stable and long-life operation of spacecraft and safe activities of human beings,but also makes new breakthroughs in the fields of physics,chemistry,material science and life science under the special environment of space enriching its scientific connotation and promoting the development of related basic science.

4.1 Numerical simulation for Materials Behavior

Maet al.[33]from Beijing Jiaotong University used molecular dynamics method to simulate the irradiation damage of GaAs material and the effect of pre-strain on the irradiation damage process.By analyzing the relationship between the number and recombination rate of crystal defects caused by irradiation damage and temperature,irradiation energy and pre-strain,the irradiation damage rule of GaAs material under Ga primary dissociated atom and As primary dissociated atom was obtained.The results can provide a theoretical basis for the protection of these materials in space application.

During the process of deorbiting,the sail must be exposed to the harsh space environment in low earth orbit for a long time.The erosion effect of atomic oxygen on the sail film material will cause serious damage to the sail structure.In order to reasonably evaluate the life of sail surface materials for off-orbit thin film sails,Fuet al.[34]established a numerical simulation model based on the experimental characterization results of sail surface pores,cracks,crease and other defects by using Monte Carlo numerical simulation method to analyze the erosion of sail surface materials by atomic oxygen at different scales of defects.The effect of atomic oxygen cutting defect density on sail film was studied.The deorbit process of a sail from 750 km orbit for 38 months is studied as an example.The calculation results show that when the sail width defect is 500 nm and 1 μm,the cut depth is 1.2 μm and 1.4 μm,and the cut width is 600 nm and 1.1 μm,respectively.The simulation results were compared with NASA’s long-term exposure test results to verify the effectiveness of the model.This model can provide a preliminary theoretical basis for the life evaluation of an off-orbit sail.

4.2 Materials Behavior in Ground Space Environment Simulator

During the operation of spacecraft in low Earth orbit,both atomic oxygen and ultraviolet radiation in space environment will affect the mechanical properties of nonmetallic materials.Suiet al.[35]studied the mechanical strength properties of nylon under the synergistic effect of atomic oxygen and ultraviolet irradiation.The results show that the material fades obviously under UV irradiation.Both UV irradiation and atomic oxygen can reduce the breaking strength of nylon materials.The synergistic action of atomic oxygen and ultraviolet irradiation can enhance the mechanical properties of monolayer nylon.The penetration of UV irradiation on multilayer nylon is weak.The mechanical properties of the warp-stitched test parts are better.

Luet al.[36]studied the effect of simulated space environment on the mechanical properties of polyurethane coated fabrics.The results showed that the mechanical properties of single-side polyurethane aramid composites decrease at high and low temperatures.However,the effects of humidity and heat,alternating high and low temperatures and combined environment on mechanical properties were not obvious.The mechanical properties of double-sided coated polyurethane nylon fibers were significantly enhanced at low temperature,but decreased at high temperature and humid heat.Similarly,the effects of alternating high and low temperatures and compound environment on mechanical properties were not obvious.

Polyimide film is an important polymer material used for the construction of spacecraft.The performance of Kapton can be degraded for atomic oxygen erosion in space.Commonly used atomic oxygen protective layers have issues such as poor toughness and poor adhesion with the film.Jiang Donghua from Tianjin University carried out relevant research titled “Atomic Oxygen Adaptability of Flexible Kapton/Al2O3Composite Thin Films Prepared by Ion Exchange Method”[37].Kapton/Al2O3nanocomposite films were preparedviaan ion exchange method,and the optical properties,mechanical properties,and mechanisms for the change in the mass and microstructure,before and after atomic oxygen exposure,were analyzed.The behavior of the Kapton/Al2O3composite film under the atomic oxygen environment of space is investigated,which provides the basis for studying the effects of atomic oxygen on the flexible protective Kapton film.

Tonget al.,from Hebei University of Technology,focused on the damage effect and mechanism of Kapton thin film under the synergistic environmental factors of atomic oxygen and micro debris[38].The performance evolution of Kapton films under the conditions of MD(micro debris),AO (atomic oxygen) single factor load spectrum and MD+AO,AO+MD asynchronous synergistic load spectrum were studied by laser driven flyer and microwave atomic oxygen technology.The macro morphology,optical properties and quality changes of Kapton films before and after each load spectrum were compared,and the mechanism of micro-morphology and structure changes was explored.

The damage behavior of Polyimide (PI) fibers under electron irradiation,proton irradiation and stresscoupled proton irradiation was investigated.Ju,from Changchun Institute of Applied Chemistry,Chinese Academy of Sciences,studied the mechanical damage behavior of polyimide fibers irradiated by space-charged particles under the condition of space environment simulation equipment irradiation[39].The tensile tests of the samples before and after irradiation were carried out by XQ-1 fiber strength tester.Under low energy and high energy electron irradiation conditions,the mechanical properties of polyimide fibers are weakly affected.Proton irradiation will greatly reduce the mechanical properties of the materials.When the stress coupling effect is increased,the effect of proton irradiation on mechanical properties is weakened.

Wuet al.[40]designed and developed a modified phosphate-bonded solid lubrication protective coating to solve the problems of surface degradation,densification and lubrication failure of organic solid lubrication protective coating exposed to space environment for a long time.The structural changes and vacuum tribological properties of modified phosphate bonded solid lubricating protective coating were analyzed by ground simulated space integrated environment equipment system after irradiation with ultraviolet,atomic oxygen,high-energy proton and electron for a long time.The results show that UV and high-energy particle irradiation have no effect on the mechanical and vacuum tribological properties of modified phosphate bonded solid lubricating coatings.Atomic oxygen has a certain oxidation effect on the surface of the coating,but it does not affect the friction and wear properties of the coating,and the coating still shows good lubrication after various irradiation.

Zhanget al.[41]prepared high stability inorganic thermal control coating by using new inorganic white filler and inorganic binder.The thickness,surface density,thermal radiation performance,vacuum volatility,thermal cycling performance,space environment stability (vacuum-ultraviolet,vacuum proton,vacuum-electron,atomic oxygen) and adaptability of various substrates of thermal control coating were tested and verified.The results show that the solar absorption ratio of the new inorganic thermal control coating is less than 0.07,the hemispheric emissivity is more than 0.90,and the surface density is 200–360 g·m–2.After ground simulated space environment test,the solar absorption ratio degradation of the coating is small,with excellent space environment stability,suitable for a variety of substrate surface.

Carbon nanotube is a kind of one-dimensional quantum material with special structure,which has excellent mechanical,electrical and chemical properties.It is an ideal candidate material for future electronic components and has a broad application prospect.When carbon nanotubes are used in spacecraft,the influence of space-charged particle radiation environment on their performance should be fully considered.Tianet al.[42]studied the effects of electrons and protons on the microstructure and conductivity of carbon nanotube paper based on the radiation environment of charged particles in geosynchronous orbit for the space application of carbon nanotubes.The results show that the degradation of the electrical properties of carbon nanotube paper is due to the change of the surface structure of the material and the increase of the number of defects in the material under the irradiation,which affects the migration path of carriers in the material and leads to the decrease of its electrical conductivity.

The preparation of suitable coating materials is crucial for enhancing the atomic oxygen erosion of zirconium alloys.Zr-Al-C ceramics composed of MAX phase have excellent inherited properties of metal and ceramic,making them useful as spacecraft materials for atomic oxygen protection.Guoet al.[43]from Tianjin University explored the possibility of applying MAX phase,a new material,in the field of space atomic oxygen protection.Zr-Al-C coatings were successfully prepared by the magnetron sputtering method.The macroscopy morphology,microstructure,adhesion and the effect of atomic oxygen of Zr-Al-C coatings were all investigated.Zr-Al-C coating could protect Zr alloy under certain exposure dosage of atomic oxygen.Meanwhile,further increase in exposure time of atomic oxygen led to the formation of ZrO,ZrO2,Al2O3on Zr-Al-C coating.Also,more pores appeared on Zr-Al-C coating surface due to the oxidation of carbon elements in the coatings to form volatile oxides,such as CO and CO2.As atomic oxygen erosion continued,the existing holes became connected to form complex channel-like labyrinthine two-dimensional network structures.The latter penetrated further the atomic oxygen into the interior of Zr-Al-C coating to continue the corrosion effect of atomic oxygen.By considering the protection effect of Zr-Al-C coating on Zr alloy under a certain exposure dosage of atomic oxygen,the protection time can be calculated and experiments can be designed according to the linear law obtained as a function of the thickness of Zr-Al-C coating.

4.3 Materials Behavior in Orbit Exposure

On 22 December 2020,the “Yuanguang” scientific experimental satellite of Hebei University of Technology successfully took off in Wenchang,Hainan province.“Yuanguang” satellite is a 20 kg space science experiment satellite.Its main load is the space tribology experiment load developed by Hebei University of Technology.Its main task is to carry out space mechanism and tribology experiment with Cubic star,so as to explore the variation rule of mechanical properties from material level,component level to system level with service time.A cross-scale mechanical model of interface micro-mechanical behavior and mechanism macro-motion will be established.The designed scientific load scheme can realize dynamic observation on two-dimensional scale,which provides a reference for subsequent space observation[44].

5 Space Experimental Hardware for Material Investigation

Experimental equipment is the foundation and guarantee of space material research.In recent years,China has established an in-orbit space station,ground simulation equipment for space environment,and a small ground simulation platform for space environment adapted to low-cost commercialization.

5.1 Material Experiment Cabinet in China Space Station

Due to the pace of China’s space technology development and the constraints of space resources,China’s space material science will mainly focus on exploratory experimental research and space experimental ability cultivation before the construction of China’s own space station in 2020.In May 2021,the station and core module completed in-orbit tests and verification.On 17 June 2021,the Chinese enter their own space station for the first time.The Construction of the China Manned Space Station will be completed around 2022.It will support large-scale and multidisciplinary space scientific research,technology verification and space application,and will have unique advantages such as astronauts participating in experimental operations,maintenance and upgrading of experimental equipment,return of experimental samples,and transmission of space-earth information.China’s space station,which will operate in orbit for more than 10 years,has ample experimental resources,providing historic opportunities for multidisciplinary,serialized and long-term space research.

The China Space Station will conduct research in the direction of space material science,closely combining application requirements,aiming to reveal the laws of material physical and chemical processes in microgravity environment,improve and develop materials science theories,and guide and promote the improvement of materials processing technology on the ground.High performance materials of scientific importance are studied and prepared and validated by space tests.These results provide scientific basis for the design and research of space component materials in the future,and make positive contributions to the formation of new material science.

The space materials science direction of the space station mainly supports the following research contents:growth (solidification) interface stability and defect control,undercooling,nucleation and crystal growth,phase separation and aggregation behavior,research on space preparation and technology of high performance materials,measurement and research of melt physical properties,materials behavior in space environment,and other space material science experiments suitable for the space station.The high-temperature material science experiment cabinet and container-free material experiment cabinet are arranged in the space station cabin to realize the above space material science research.

The high temperature material science laboratory cabinet supports the research of material preparation process mechanism under microgravity,material preparation and research of important application background,and other relevant material experimental research.Scientific experiments on melt growth and solidification of metal alloys,semiconductor optoelectronic materials,nano and mesoporous materials,inorganic functional materials and other materials have been carried out in the form of ampoule structure encapsulation.

In the containerless material laboratory cabinet,the research on the mechanism of the material preparation process under microgravity,the material preparation and research of important application background,and other relevant material experiments were completed.The containerless processing is realized through electrostatic suspension technology,and the research on containerless processing of metal and non-metal materials under microgravity,deep undercooling of materials,and thermal property measurement of material melts are mainly carried out.

In addition,some space material exposure tests need to be performed on the extravehicular exposure test unit of the space station.These space material experiments mainly include space damage and service performance experiments of space application materials (lubrication,thermal control,film coating,shape memory,functional coating,polymer,composite materials,etc.),tribology and other cross studies.

5.2 Ground Simulator for Space Environment

The first space materials and environment engineering laboratory of China was established in Harbin Institute of Technology on 27 February 2000[45].On 28 January 2005,the National Defense Key Laboratory of Materials Behavior and Evaluation Technology for Space Environment was established,mainly carrying out basic research on interaction between space environment and materials[46].In China’s 12th Five-Year Plan,Chinese scientists further put forward the idea of building a ground simulation device for space environment.On 29 August 2017,the project officially started construction.On 10 July 2021,the thermal vacuum test of the integrated radiation simulation test module and the lunar dust environment simulation test module of the integrated environmental simulation system of “Space Environment Ground Simulation Device” was successfully completed.At the same time,two typical environmental factors of solar system vacuum and low temperature can be simulated on the ground.

Ground Simulation Device of Space Environment of Harbin Institute of Technology is the main installation of national science project based on comprehensive simulation of many space environment factors[47].The device can realizein situ/semi-in-situcharacterization of the interaction process between space integrated environment and matter,and study the coupling effect mechanism of multiple space integrated environment on the same platform.By exploring the spatiotemporal evolution theory of performance/function degradation of materials,devices and systems in space integrated environment,the evaluation theory and method of on-orbit reliability and life of space materials,devices and systems will be established.As a whole,the facility will build a world-class simulation platform for space integrated environment (vacuum,high and low temperature and alternating,plasma,weak magnetic/zero magnetic,particle irradiation,electromagnetic radiation,atomic oxygen,molecular pollution,etc.).At the same time,the facility is equipped with many advancedin situand semi-in-situanalysis and testing devices,forming the most complete conditions and capabilities in the world for the study of space environment and mechanism of interaction with matter.The “ Ground Simulator for Space Environment” national Science project of Harbin Institute of Technology is composed of space integrated environment simulation and research system (including integrated environment simulation subsystem,space life science subsystem,micro mechanism analysis subsystem,ion accelerator subsystem and device ion irradiation subsystem),space magnetic environment simulation and research system,space plasma environment simulation and research system,numerical simulation and ZY monitoring system and supporting system,etc.

5.3 Low Cost Small Space Environment Simulation Platform

At present,large space environment ground simulation equipment in the world is based on the principle of ground reproduction of space environment.By reproducing the real space environment as much as possible,the action mechanism of materials in the simulated environment is the same as that in orbit[4].The sameness or similarity between simulated environment and real space environment is emphasized.This research method has high engineering reliability,which helps to reveal the basic law of material structure evolution under the action of space environment,and provides important scientific support for the reliable,stable and long-life operation of spacecraft and human safety activities.

However,the operation cost of large-scale ground simulation equipment for space environment is generally high,which requires strong support from the state to carry out relevant research.For a few individuals or groups,it is difficult to carry out space science and technology research because of lack of funds.Especially in recent years,with the rapid development of commercial spaceflight,the miniaturization of spacecraft will be a development trend.Micro-satellite is a new generation of spacecraft with clear purpose in space science and technology,which has shown great application value.Many scholars have proposed and are carrying out research on small-scale ground simulation devices for space environment[48–50].At present,many small sample service behavior and commercial space materials service evaluation test requirements appear in the research and development of new spacecraft materials.The ground simulation method of space environment has gradually changed from the principle of reproducing space environment factors on the ground (oriented to environmental factors) to the principle of studying the consistency between ground and in-orbit (oriented to material factors) of the main properties and mechanism of materials.

The single-particle effect on spacecraft is mainly caused by heavy ions and protons,and protons also produce heavy ions through nuclear interaction with semiconductor materials and then induce single-particle effects by heavy ions.In the process of simulating singleparticle effects with pulsed laser,although the laser is used as an environmental factor,which is quite different from the heavy-ion environment,the physical mechanism generated in semiconductor materials is similar to that of heavy ions[51].At the same time,atomic oxygen does not exist in the form of neutral atomic oxygen in the ground atomic oxygen simulation methods of ion beam type and plasma type,but its response mechanism is similar to that of space flight tests and experimental phenomena and reaction laws can be obtained.The space atomic oxygen equipment developed by Beihang University belongs to plasma type[52].Yanget al.[53]took ozone as the corrosive medium and realized the relative scouring of samples by high-speed relative movement.Similar phenomena and laws were also obtained.

6 Summary

From 2020 to 2022,the rapid development of China’s space industry has promoted the further and more integrated development of materials science research in space field.With space environment as the link,Space materials and Aerospace materials are further integrated to form three research directions including Materials Sciences in Space Environment,Materials Sciences for Space Environment,Materials Behavior in Space Environment.Multi-level space material infrastructure and experimental equipment will be built,including China’s space station,ground simulation equipment for space environment and small low-cost ground simulation platform.It will enable more scientists to participate in materials science,space technology and earth science research,and promote the integration and development of machinery,artificial intelligence,big data and other disciplines.